C1 compatibility with Mac OS 11.4 & Canon MK II firmware and cost

Looking at moving from an old version of Lightroom (LR5) to C1 and a few questions that current users may assist with:

1) Considering buying a perpetual licence which I see offers lower cost upgrades when they are available. Does can anybody comment on the cost of the upgrades when they come about and is it possible to jump across upgrades (eg - miss one and go to the next when it is released)

2) How often do new releases come about and when was the current version released

3) Are there issues with working with Mac OS 11.4

4) Any issues with compatibility with Canon 5D MKII on firmware 2.1.2 which I believe is the current (albeit many years old) release for this camera

Thank You