Yes :)

You DO need to buy a ticket in contradiction to Kalmec's suggestion that it is free. It is a very small amount, only W1,000. You could dodge payment if you wanted to, but why? There is also an combined ticket with the Suwon Hwaseong Fortress itself, Hwaseong Haenggung Palace and Suwon Hwaseong Museum for W3,500. You can easily do all 3 on a day trip from Seoul. Check the tourist office in Suwon (left out of train station) and they will provide with details for the bus you need from the train station plus a map. 100% recommended as a great day out!

Assuming that you will take train to Suwon station..and then a bus or cab to hwaseong fortress which is approx 5 km from Suwon station. The perimeter of wall of fortress takes approx 2 hr to walk and has 4 main gates. There is also a bus to give a tour around the wall. Hope this helps.

창룡문 주차장이 있으며, 장안문 옆에 공영주차장이 있습니다.

It never closes, only the attractions around it (ie 5PM). Best time I like to visit was late afternoon, early evening to see lights displaying wall in certain areas.

I think it will be opened during Chuseok Holidays.

While you could walk to the fortress, I find it better to take a bus to avoid losing my way in the heat or freezing weather, depending on the season you are in. Save energies to walk and explore the interesting markets and exterior surroundings of the fortress too. It is very easy to take a bus from subway station to the fortress and vice versa - the bus stop is just 50m or less from the tourist promotion board right after you stepped out from the subway station, and on the same side of the road as the tourist promotion board. Short ride and you will notice the prominent gate to alight. However, on return trip, you may not exit from where you enter into the fortress. So, you can either circle back to where you enter, which will be a long walk, or simply take a return bus on the same side of the fortress. There will be bus time tables pasted on the bus stop to ensure you are on the right side of the road for return leg, at least that's what I saw on my return leg. :) If in doubt, ask at the booths located at edges of the fortress. Do remember the bus station landmarks where you board to travel from the subway station to the fortress, because the return leg is a loop through other roads, and does not pass through the same roads. So, remembering the landmarks around your "first bus stop" where you board is important. Hope this helps.

The price is KRW 3500 per person to visit all parts and the palace. But on Cultural Day, it's free, but the attractions are closed. 25th March it was a Cultural Day, so we couldn't visit the inside of some buildings.