Yeah, I brought up #1 last time this was posted.

As for #2, mechanics who get into F1 teams get in because they're elite mechanics. And, you don't become an elite mechanic without getting your hands dirty on a normal consumer-grade ICE car. Now, it's true that modern consumer-grade cars have lots of electronic systems that require special diagnostic tools. But it would be ridiculous to suggest that an F1 mechanic couldn't handle most of the standard maintenance tasks.

Now, what I could imagine is that an F1 mechanic might not want to spend their free time working on his own, or a relative's car. Part of that is not wanting to do in your free time what you do for work. Part of it is doing work for free. But, I imagine a big part of it is the pain of working on a badly put together piece of crap. A F1 car is a work of art. The engines only last about 8 races, which is less than 24 hours of running. An F1 engine isn't going to have any real buildup of gunk. Any loose parts will have been loosened from 2 hours of hard racing, not 5 years of sloppy maintenance. There will be massive amounts of documentation on every part in an F1 car, with engineers on call if you ever have questions. Working on a relative's car is probably like working on an old POS computer with an outdated OS with all kinds of pop-ups, etc.

OTOH, I imagine a lot of the F1 cars are sometimes a pain in the ass to work on. Everything is designed around performance, and nothing is designed around ease of maintenance. There are probably a lot more sharp edges you can cut yourself on, nothing that's easy to access like a dip stick or a washer fluid port. Plus, every time you're working on one it's with a big team in a high-stress environment. So, I would bet that sometimes an F1 mechanic would want to just slowly work on their own car at their own pace while listening to music or an audio book or something, rather than having the chief mechanic demanding updates etc.

So, in the end, I bet most F1 mechanics can fix most of the issues with their own cars or with relative's cars, but mostly they don't want to. They probably do fiddle around with their own cars sometimes when it's fun. But, if it feels too much like work, or it's frustrating, they'll just take it to a "normie" mechanic so they can enjoy their time away from the track.