Well, mathematically speaking, there is no difference whether or not you are playing one slot or moving around the casino. Due to the fact that slots are built around RNGs, and the consequence of every spin is totally arbitrary, you'll get the same fate whether you play at one slot the entire day, or move around.

It does not matter. The machines are programmed to take money from you. If you are lucky, you might have one return more money than you put in for a while. There is no system or other way to beat the long term fact that the house always wins.