Do you have to make a reservation

No, but I strongly recommend that you do, so you get the campsite you want.

You do not have to make reservations but is highly encouraged, is a busy park during the spring to early fall season. If you are just going to do a picnic they have many first come first serve areas. Large gazebos and group areas if they are available you can pay for on the day of (i have many times) but you run the risk of not being available if you dont plan ahead.

For camping- yes. For strictly day entrance- highly recommended, especially on holiday weekends

You absolutely must for an overnight stay, for a day visit, I am not sure. Usually reservations are made months or weeks ahead. It is totally worth it. Loveliest place! Communicate first

There busy , just be prepared..

I think it is suggested since I did see some spots at said reserved and others said available so you may be able to go without making a reservation and if one is available grab that spot. Hope that info helps