system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] The blood games

Greetings noble citizens of Terra. I am one of the noble Custodes, and definitely not an Alpha legion infiltrator. For this iteration of the blood games we wish to simulate a mass attack on the palace by normal humans. I need as many as possible to assault the palace like your life depends on it, which I promise is totally not the case. The Custodes will be using training weapons and will definitely not murder you my the thousands. Anybody who cam make it to the throne room without getting "tagged" by a Custodian or the palace defenses will be permitted to gaze upon the Emperor himself atop the golden throne for a whole ten seconds, so really try to get in there!

For the purposes of this exercise we have produced millions of training weapons like human scale bolt guns and grenades. The effects are very realistic, so don't be worried if it looks like anybody is getting horribly maimed and/or killed, it's all part of the exercise!

Me? Yes I'm a real Custodian. I'm wearing armor because I'm outside, and I'm outside to talk to you people. Yes, I know we never come out, like I said I'm out here to announce this holy task to all peoples of Terra. The device on my pauldron? It's, umm, a dragon? Yes, a dragon and definitely not a Hydra, because like I said, I am definitely not an Alpha Legionnaire, and definitely not planning to assassinate the Emperor.

So go on people, fight with all you have, and make your Emperor proud!

(Ooc for the actual question) Would the entire population of Terra, armed with many many weapons, be able to gain entrance to the throne room? 

And, if they did, would an embedded Alpha be able to kill the Emprah?
gpt
It depends on what you count as the population of Holy Terra. If you count the High Lords and allow them to utilize their resources, then yeah. If you're just talking about the common hive rabble, then the answer is a resounding no.

An embedded Space Marine of any kind, loyal or traitor, could probably kill the Emperor if he is alone on the Throne. With any number of Custodes guards, no, probably not.