Assume the communication with the app it through Internet. The car must have a 4G chip (too early to see 5G in cars, I think?). So no matter what you pay, it won’t work when 4G is retired. With marketing pushing to get new standards always faster, 4G may not last another 20years.
Anyway, bear in mind that once you subscribe, they will most likely collect detailed data about how you use the features and sell that as well…
In theory, yes, you could make a mess, and any firmware is supposed to be certified to allow the device to be used.
In practice, this has been a convenient excuse to keep a whole chip with a separate OS in every smartphone, and it is very difficult to isolate from the rest of the system (see Graphene OS efforts).
I say all firmware should be opensource. Whether you’re allowed to change them or not is a separate question… for now.
Half of the job is to fix issues with existing suff, the other half is to make working stuff more complicated and problematic (aka “upgrade”), so that we’re still paid to do the first half.
I kind of hope it’s real. Down that path at some point they’ll decide the whole Internet and all modern technologies are satanist and leave Internet for good. They can embrace the Amish lifestyle, it’s a win for the rest of us.