There is always a starter's area either in a tent or the clubhouse depending on the venue and it is a requirement to check in officially and get your card the day of each round. Generally, other rules or information is passed to the player on the practice day or Pro-Am day.

It's up to the player. Generally they point or their caddie does, but at tour events there is usually a crowd reaction as well.

There is always a rules official nearby who can be summoned to make a ruling if needed.

It is not required to summon a rules official or check with his competitor although they generally do the latter out of safety and courtesy. The player can make the call himself and often does if it is clear cut. If there is some doubt, he will usually consult with his playing partners. If they are still in doubt, he will summon a rules official. The key here in golf is that it is up to the player to know the rules and make the correct play. If he makes the wrong one, the penalties are significant loss of strokes and/or even disqualification, even if his playing partner agrees with his action. That's why they call rules officials when there is any major confusion. Many times, the player makes the call, goes ahead and plays and does it correctly and there is no problem. However, if his playing partner disagrees or sometimes even people watching on TV do, he can be retroactively penalized later.

These days, for 99% of the players the money is direct deposited in an account they have given the PGA for that purpose. Ocassionally with a newcomer, that account might not have been set up and they give him a check, but that is rare these days.