Chuckles, boarding can start anywhere between 11am and 2pm. It just depends on how quickly the previous cruise clears. You won't be able to go to your room before about 1pm, even if they let passengers on the ship before that.
If you like more flexibility in dining time than the set main or late seating, Anytime Dining may be for you. If you like the idea of having the same waiter and the same tablemates every night, and same dining time every night, traditional seating sounds better suited to you.
On formal nights, men usually wear a suit or at least a blazer and tie, and women wear a dressy dress or pants outfit. There is a lot of variation in what folks wear, and usually an alternative place to eat dinner if you don't want to get dressed up.