You must play on hardcore or insane the whole level without changing for it to be there. It is located on Haestrom in the recruit tali mission. it is on the floor in the room that tali is located in.
Most likely because in demos the player is seen fighting Husks which are created by the Geth
reapers, geth and cerberus
There is a location where you can operate door controls. You make certain pressures add up to enough that the door will be able to close and sever one of the claws. It's in the last location of that level, the area with the geth Juggernaut.
While the Geth and Sovereign are attacking the Citadel, You will be prompted with a choice to either have the Alliance attack Sovereign or protect the Council. You need to protect the council.
The collector rifle can be found in the collectors edition or in the Recons Operation Pack
resuce him from the derelict reaper on your IFF mission. then reactivate him in the ships A.I. core. (doesn't really make sense to put a geth in the ships A.I. core if everyone is so distrustful of it)
It depends on the planet! All masses are different on each planet, because the gravity is different. But I'm sure you want the weight of them in Earth terms. They're about the weight of a human, only a little heavier, as they are machines.
Later on in the game you will unlock spetre requisitions. This allows you to purchase the rifle for a staggering price of at least 250000 credits
If he died in Mass Effect 1 then he is not in Mass Effect 2. If he survived Mass Effect 1 he shows up in Mass Effect 2 but he can not be killed.
The assault rifle you get from it is pretty strong other than that there isn't much special about it. Tip this into google "See the Mass Effect 3 Collector's Edition Unboxed, Complete With Robotic Dog! GameFront" and you will see that it all you can get!
Your class has to have the primary weapon set to the sniper rifle. If it is then clicking the right analog stick should zoom on default settings.
The effect of mass extinction is extinction, death of a mass