Hello and Welcome To BYC! At two days most people want their chicks to have food in front of them all the time. Regular chick usually don't overeat, Meat Birds usually are put on a feeding schedule when they are a little older. Be sure to check out the Learning Center, lots of great articles on chicken keeping https://www.backyardchickens.com/atype/1/Learning_Center
What kind of chicks are you raising? As Kelsie said above, there is a point where that (meat bird or not) can come into play - but at the moment, you do want food available to them at all times.
Yes, 24/7. They need to eat when they need it and will stop when they don't need anymore. Always keep fresh water and fee available at all times. Welcome to our flock!