I'm starting P3R, any advice?

I've already played P5R & P4G, and I'm excited to play this one, I have a few questions:

1-Any way to get money and XP fast?

2- If there’s a “true” ending, how do u get it? (keep it spoiler free)

3- from what I’ve seen, this game happens in one big “thing”, it doesn’t has any “palaces” or something like that (I think) but does it has any deadlines?

That’s all, bless you all