EU will likely want something like this for ChatControl (or whatever it's called in its current draft iteration) enforcement anyway. And Google will no doubt be happy to have its highly paid lobbyists testify on how it will help catch child predators and terrorists.

Marginally. Apple still approves every app that runs there and can block whatever they don't like for whomever they don't like (or are told to block by a US court, for example). And if you go on holiday abroad and want to take your phone, Apple refuses to tell you what the grace period is during which you're allowed to use the apps on the device.

It's as hostile as they can make it because people apparently keep buying that, even when there's no semblance of the freedoms we have on Android, Windows, Linux, BSD, etc. Google saw that this suffices for the EU and does half a step towards it and people are, unsurprisingly, appalled because the whole FOSS community is here now. I still think it started with Apple demonstrating how successfully hostile you can be in a duopoly where the cards have been dealt.

Few commercial entities will happily re-implement their apps for a third, new, upcoming platform. Google and Apple will never get outcompeted so long as their software ships on the hardware that people want. Even Microsoft (Windows Mobile predated both OSs) threw in the towel, I wouldn't know who else stands a chance. Regulating these entities seems the only path when Google has evidently decided there's no point trying to compete on openness (also demonstrated by the widespread acceptance of GrapheneOS in the FOSS community: people would rather be kept safe than be free - https://news.ycombinator.com/item?id=48758146)