You have to fly as much as they tell you to. You will get paid at least 75 hours, regardless of how much you actually fly. Many majors have a max monthly credit (unless you volunteer for more) but few or zero regionals have a max.

Credit and block are not the same. The FAR 117 limits apply to block, not credit. So activities like training and deadhead will pay credit but are not block.

Also trip rigs specify that for a certain amount of time away from base, and on duty daily, you will get paid a certain amount regardless of how much you actually fly.

All airlines *should* pay you for cancelled flights...if you you stumble on one which doesn't, run away fast.