> You don't have to deliver your PC game through Steam, and many of the big publishers have opted not to.

A better analogue would be that you download WoW free from Steam, then take a subscription at Blizzard. Does Steam allow that?

no, again, this would only be a reasonable analogy if there were _any other way_ to download software onto an iOS device, which there is not.

It's not Apple's _dominant_ position as a delivery mechanism that counts - it's their literal monopoly on it.

I've uploaded 3rd party CD keys to steam and they've allowed me to download the game (multiple times) and stored my saves etc...

That’s only if the publisher allows that, or in many cases these are “Steam Keys” which are sold in emerging markets where credit and debit cards that can be billed internationally are quite rare.

Yes. Just because you bought a game on Steam doesn't mean you have to purchase all additional content through them as well. Steam installs full-fledged applications directly in the OS, not locked down sandboxed apps like on iOS.

AFAIK if you bought the game from steam all subsequent micro transactions form that account/client still incur a fee to Valve.

The Steam apps are “sandboxed” as in you cant run them without Steam, they use their own executable that is tied directly into Steam.

Steam will get a cut, they have different rates for conversions and micro transactions.

You can buy CD keys from other websites to activate a Steam game, so yes.

Publishers pay for allowing retail key linkage and in most cases today you are buying Steam Keys from markets where these are sold in stores instead of a retail version and Steam gets a cut.

    Steam keys are meant to be a convenient tool for game developers to sell their game on other stores and at retail. Steam keys are free and can be activated by customers on Steam to grant a license to a product.

    Valve provides the same free bandwidth and services to customers activating a Steam key that it provides to customers buying a license on Steam. We ask you to treat Steam customers no worse than customers buying Steam keys outside of Steam. While there is no fee to generate keys on Steam, we ask that partners use the service judiciously.

https://partner.steamgames.com/doc/features/keys

It seems like this is not the case.