You can try using the same brand again or you could try Michelin Pilot Sport. They're really decent tires and handle really well.
Try restarting your app after changing your tires to see if it removes the message.
That's really annoying. That's why I bought a seat belt locking clip.
Bought mine from Amazon. You can choose here
https://www.amazon.com/seat-belt-clips/s?k=seat+belt+clips
It should be automatic. To set up your Digital Key, go to your BMW ID settings on the screen, locate the 'Keys' options, and check the box to add the Digital Key. If you use your phone as a key, your car will automatically recognize you.
The i5 M60 has rear steering and active roll stabilization, but I'm not sure if it has rear climate controls, which may be available in other countries as part of a package. I can't find any information about this feature in the papers.