The Age II building "Indian Allies" says to immediately place 2 soldiers in one of your colonies. I understand that part. I do that as soon as I pay for the building.
But, do I get to place another two soldiers on each following turn during the capital building benefits stage? Or, is the initial two soldier placement a one time use?
No, it is a one-time effect. Hence the word "immediately". The absence of the words "each turn" is also a give-away.
In the age III buildings, there are several that say something like this: "2VP per soldier in the new world" or "4VP for each merchant ship owned"
Are these VP's scored on every turn during the capital building benefits stage, or are they scored just once after turn 8?
All VPs for capital buildings are only scored at the end of the game.