Staying After Working Hours

Hi. I'm a student and I've started working in the old place again. Not that I was pleased (they stopped by salaries), but the supermarket itself is not particularly large and I am used to the place itself, colleagues and customers. I work as a cashier. The first time I spent two months, but I started the session and used it as an excuse to leave, and I got out of the way because of my salary cuts. I worked at 4:00, then I was that old. I didn't want to say why I was leaving so I wouldn't get extra nerves in the last working days with the managers (one of them was pretty nasty). A few days ago, I came back again, because for a month I was looking for work, putting on the pocket, on Facebook I wrote, I went around the city asking in the shops and coffees and nothing. In the end, one of the managers texted me to try again, and I accepted. However, tonight we closed 2h early (for me 1h, because I work until 9) and started cleaning the store, but mainly cleaning. It was very dirty, probably untouched for at least one or two years. So I got home at 00:00. I don't have a problem staying, good thing it was a day off. My question is should it be compensated in any way - with payor rest as hours are working after working hours? I am unlikely to take the issue to the managers, for the simple reason that we all stayed except for 3 people on the staff (1 is sick, one manager was not there and a colleague who never understood why she did not stay after all the others we were left). The other thing I want to ask is, can we get punished or fired because under one of the crates we found an envelope with little halves and we took one with our co-workers because we hadn't eaten anything, and I was easily bloodied. Just when we chewed them up and almost everyone came together and one of the managers asked what the colleague ate (I don't think she saw me) after we locked up and didn't pay (and it costs 20-30 pennies maximum). The co-worker said she took it from her, not the store. But if they see the cameras, you can see how we get one (even though it's not from the counter, but they were under the till forgotten by God for sure). Not to mention that colleagues keep getting candy, sweets from the window, etc. It's the first time I've allowed myself something like this, I just really feel bad when I don't eat. I know it's not right, but... What am I supposed to do, I acted instinctively. I'm afraid I'm going to get fired because I really don't have anywhere else to go, and I need the money.