Yes, their flagships are great. I used them exclusively since the Z1 up until I got a Pixel for super cheap and a year of unlimited service thrown in. Not sure what the dev scene is like these days but part of the reason I switched was because it was pretty much stock Android which is what was modding the old phones to get to anyways, so I didn’t really follow it after switching.
I do know that their bootloaders are unlockable though.
No idea, but since Google fucked over Pixel 8 and 9 users anyways and took it away I’m not overly concerned about it.