Hello. There are builds for PC and builds for Android (.apk). If you have an iOS phone you won't be able to play it on it though unless you have Steam and stream it to your phone.
If I understand you correctly... if you purchase the game once you will own it forever and get all updates to the main story of the game from that point forward.
Am truly sorry 馃槥 I get confused alot sometimes was wanting to ask when I pay for chapter 3 is that chapter 1 of 3 full game and can I play on my phone and pc am very sorry the game play i played so far is awesome