I'd like to take a week or so to go hiking and camping when the weather gets warmer but I have no clue as to what I can and can't do legally, so I'm after some advice to keep me out of trouble as much as possible:

-I'm told I can't legally wild-camp in England, but in Scotland it's fine. Is that true, and if not, what are the laws on that now?
-How do I make sure I'm not trespassing on private property if I'm in a place where wild-camping IS legal?
-What does the law allow me to do with regards to making small fires/using stoves?
-Supposing wild-camping IS illegal all over the UK but there are still places I can hike, does the law forbid me from just sleeping under a tree without a tent, and would I still be forbidden to use a stove to cook meals?
-Any other information and advice you can give me would be great, thanks!