IAP For All Platforms?

I’m working on setting up in app purchasing for my game but a few thoughts come to my mind. Please feel free to correct me if I wrong but I see some limitations:

  1. If I create a game and I port it to Linux for example. How/What IAP can I use? Its not a windows product so I cant use Windows store, its not Mac so I cant use IOS and clearly not droid so I cant use Google Play store. Only option I can think of would be Paypal but does paypal support this concept?
  2. I also want to port to Mac (desktop). Can you use the IOS store for IAP for a Mac desktop?
  3. Is there a all in one solution for IAP? I would really prefer to just setup one account in one place and process all payments though that IAP store. I only plan on using IAP for Game Currency so I don’t need anything complicated. Anyway does anyone have answers to these questions? Thanks. Videos also would be very helpful and links to articles.

Have you taken a look at the IAP docs?

Specifically, the cross-platform guide seems to cover your questions. Though I’m not sure Linux is currently an option.