Did he serve breakfast, lunch and supper? or just breakfast and lunch?
I mean that was some loooooooong hours for all 4 of them to be on their feet.
Was he open 7 days a week or did he close on the weekends?

It was said on the show that he was closed on Sundays. Remember that episode when the girls had that time clock to deal with and they cleaned out the storeroom on Sundays? They stated since they had to clock in on their day off, it was overtime. And it was shown the restaurant did serve breakfast. I think Alice even mentioned the hour of 7 a.m. as the start of her work day, I am not sure, but I think it was in the episode when she moonlighted as a singer.

Did he serve breakfast, lunch and supper? or just breakfast and lunch?
I mean that was some loooooooong hours for all 4 of them to be on their feet.
Was he open 7 days a week or did he close on the weekends?

I always wondered that myself. There was one shift and no one came in to relieve them.

Question: What were the hours? Answer: Whatever was convenient to the storyline ;)
I think that's about the best answer. It's obvious they served breakfast, as Henry was there almost every day for breakfast. They were there for lunch, and sometimes they were there after dark. You almost never see one of them not being there (although I think the episode where Flo was staying with Alice, Flo didn't have to come in until later). They weren't open on Saturday nights, as evidenced by the 3rd season episode where Mel decided to stay open late and the place got robbed.

I always wondered that myself. There was one shift and no one came in to relieve them.
I always got the feeling they worked 8 hour days, 5-6 days a week.

A recent episode had one of them state they worked an 8 hour day, but if you add up if they were there from breakfast and often times when they got off it was dark--that sure seems longer than an 8 hour day.