one bucket should be enough

it is if you have really low alcohol tolerance

If they don't drink a lot and are very small in size or they drank on an empty stomach.

It is

Depends on the beer and the person drinking. Some people have a condition that frementates food on their gut into alcohol as soon as they touch a drink it'll push them into a heavily drunk state.

Everybody processes alcohol differently.
Quite possible.
Even if you're a hardened drinker, if you drink at altitude......wouldn't take much !

yes add some sugar in the can

Yes. If you're really tired and hungry.

One beer keg you mean, ... yeah

I think it would be possible if they were small, not used to drinking and had some type of liver dysfunction.