Broadly speaking, yes, having a mentor is a good idea. However, finding a mentor, a good one, is pretty challenging.
I feel like the pragmatic solution is just to try and find a good team. A good team will provide a learning environment for all of the best practices and technical skills.
There are a few mentor sites, but honestly, I've had pretty hit or miss results with them. You'd likely have to do some trial and error before finding the right fit.
Anecdotally, it would seem so.
I think it depends on the root of the hatred. An awful lot of hatred comes from ignorance, and when people dispell the ignorance, the hatred follows.
But sometimes the hatred is so fundamental to someone's lived experiences that even if it's obviously wrong, it's absolutely true to them. In those cases, I suspect it would be harder to let go of it.