You're line B has a missing move by white, I'm assuming you meant 1. Nf3 d5 2. g3 Nc6?
"the opponent can do whatever he/she wants"
When you play the KIA, unfortunately, this is going to be the case for the most part, it's just not forcing enough, but what you get in return is positions you may understand better.
I'm not familiar with 1. Nf3 lines, but A) looks like a King's Indian defense with colors reversed, and B) and C) looks like a Pirc with colors reversed, D) is too early to tell.
If you study some KID/Pirc games, it might give you some ideas.

Hello. I'm looking for some advice. More particularly, what should I do in the following lines if I'd like to reach a playable KIA:
A) 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 - should I really carry on with 4. 0-0 so that I get 4. ... e5 ?
B) 1. Nf3 d5 2. g3 Nc6 - and ...e5 seems to be coming again
C) 1. Nf3 Nc6 - the same issue with ...e5
D) 1. Nf3 Nf6 - and now after 2. g3 the opponent can do whatever he/she wants (while I'm already devoted to fianchettoing my bishop)
In general I am worrying about (1) the opponent playing e5 (I've heard KIA is not playable in such a case) and (2) the opponent playing symmetrically (KIA vs KID). What are proper plans for such cases?