Is targeted killing legal? I have read on wikipedia that for every adult the (U.S) targets on average 9 children gets killed, Trump ordered a strike on Iranian Military Leader in Baghdad. is targeted killing legal or atleast in this case? can those who perform these operations be arrested and prosecuted? can a new war begin between the two countries? (https://www.google.com/amp/s/www.wsj.com/amp/articles/leader-of-iranian-revolutionary-guard-s-foreign-wing-killed-11578015855)
Whether or not a war between political entities can result from some action is completely political and strategic, and not legal. The specific incident is probably legal, given US and international law regarding military action. Unless the order was self-evidently unlawful there is no possibility of arrest and prosecution under US law, however there might be a framework for legal action by Iran, if e.g. a drone operator were to fall into Iranian hands. The specifics of the order are not generally known, though we know that DoD states that this was due to a presidential order. This article discusses targeted killing from a legal perspective. In the context of war, killing is legal though not entirely unregulated. There was a failed attempt to sue the US in the case Al-Aulaqi v. Panetta, which involved a targeted killing of a US citizen involved in planning terrorist attacks, a suit which was dismissed. One problem is that the suit "failed to state a 4th Amendment claim", and also failed to state a 5th Amendment due process claim since Al–Aulaqi's deaths was unanticipated. The court notes that a Bivens claim allows damage action against a federal officer for violation of clearly-established constitutional rights. However, No case has discussed precisely whether a plaintiff can proceed on a Bivens action that claims deprivation of life without due process based on the overseas killing by United States officials of a U.S. citizen deemed to be an active enemy. In the discussion, the question arises whether special circumstances counsel hesitation (Doe v. Rumsfeld and citations therein), which the Doe court notes would "require a court to delve into the military's policies", and they will not do that lightly. All of this is about US citizens. Soleimani was not a US citizen.
Anyone has a right to report illegal activities that it is aware of to the authorities. This is in fact where 99.9% of police investigations start. In addition, students of a school (or, more generally, members of any organisation) are eligible to be investigated/disciplined by the school in accordance with the rules of the school providing that the investigation and punishment are in accordance with the law. This would normally permit (require?) notification of any child's parent or guardian. In loco parentis does not arise - the school is acting as a responsible citizen; not as a substitute for the children's parents.
They could be prosecuted in any state where there was evidence that part of the crime was committed. Realistically, either State A or State B could prosecute for conspiracy to murder as an additional charge, because the conspiracy clearly spanned more than one state, even if they can't prove where the crime was committed, although physical evidence (e.g. traces of camp sites, footprints, testimony about landmarks, evidence of poop with human DNA from the victim in it), would usually make it possible to show that some part of the crime was committed in the state. There is probably also a federal crime that could be implicated such as "murder involving flight across a state line" (hypothetical, but I'm sure that there is something similar on the books). I'm not going to address the further hypothetical as it is too bizzare and law is ultimately very context specific. Find a more plausible fact pattern, perhaps with a different crime, and ask a separate question if you want to really address the issue.
The means and motivation by which you intentionally harass people are no defense. There is no material difference whether you harass someone yourself, ask someone else to harass, use a drone or trained/tamed animals. Whether you harass because the target may subjectively deserve so also makes no difference. The legal repercussions stay the same: charge, trial, conviction, sentence.
It is not the case that treason must be tried by a military tribunal. See for example US v. Kawakita, which was an ordinary civilian jury trial. I cannot even imagine why one would think that there is any such requirement. Here is the federal law against treason, and nothing says "offenses must be tried in a military court". Perhaps that misconception was based on the use of military tribunals during the American Revolution, which preceded the creation of a US legal system.
No, under US law, it is an "executive agreement", not a "treaty". The vast majority of US's international agreements are done as executive agreements, and not treaties; and the power of the executive branch to make executive agreements has been repeatedly upheld in the courts. Specifically, there are two types of executive agreements: "Congressional-executive agreements". These are the ones that require changes to legislation to be implemented. Congress passes the needed legislation just like any other normal legislation, i.e. a majority of both houses of Congress. Most trade agreements are passed as congressional-executive agreements. "Sole executive agreements". These are the ones that do not require changes to legislation to be implemented. Congress is not involved at all. This Iran nuclear agreement is a "sole executive agreement" because it does not require Congressional action to be implemented. (So it doesn't need to be passed by a simple majority by Congress.) The President already has the legal authority to implement all of the US's obligations under the agreement, which are the relief of certain Iran sanctions. Some of those sanctions were implemented by the President, and which the President can remove by himself. Some of these sanctions were implemented by Acts of Congress, but those Acts specifically give the President the authority to waive them. The Iran Nuclear Agreement Review Act of 2015 (the "Corker bill"), passed by Congress in May 2015, also confirms that "It is the sense of Congress that: [...] this Act does not require a vote by Congress for the agreement to commence;" As to your question about whether something can "have the effect of a treaty if it's passed by a simple majority". The answer is yes (in the other way around). The Supreme Court ruled in the Head Money Cases that "treaties" (ratified by 2/3 of the Senate as specified in Article II) have the same legal effect in US law as regular legislation passed by Congress (by a simple majority of both houses), which means that Congress can modify or repeal (insofar as US law is concerned) any "treaty" that is ratified by the Senate, by passing a later law that contradicts it, just like it can with regular legislation. So, yes, any regular legislation passed by a simple majority (including for congressional-executive agreements) has the same legal effect as treaties.
If I were a federal prosecutor (which I'm emphatically not), I might try to charge you under 18 USC § 32 (a) (5): a) Whoever willfully— [...] (5) interferes with or disables, with intent to endanger the safety of any person or with a reckless disregard for the safety of human life, anyone engaged in the authorized operation of such aircraft or any air navigation facility aiding in the navigation of any such aircraft; [...] shall be fined under this title or imprisoned not more than twenty years or both. Since you clearly know, or believe, that this has the potential to interfere with piloting, which would obviously be a serious danger to people on board the aircraft, I'd argue you would be acting with "reckless disregard for the safety of human life." If your conduct results in anybody's death, then life imprisonment and/or the death penalty are also on the table, under 18 USC § 34.
Unless there is enough evidence to convict one or more of the suspects, none will be convicted. In general the argument: We know it must be one of you, but we don't know whch, so we find you all guilty. is not allowed in any non-dictatorial jurisdiction. Just how much evidence is needed for a conviction varies by jurisdiction in theory, and by judge or jury in practice. Also, it would be possible to charge several of the residents with having acted jointly in the crime, but there would still need to be sufficient evidence against each defendant to obtain a conviction.