Looking for a decent milling tutorial

I'm hoping to get started with a Taig CNC mill soon for quite a few projects, probably with Mach3.
I have not done milling before and can already see some obvious questions.

I have a 2D part that needs to be cut out through the entire depth of the aluminum. How do I keep the mill from striking the XY rails underneath? Stick plywood underneath it or what?

Say the part's a circle (it's not, let's just assume) cut out of a square. Obviously the part's going to become loose & bendy partway through and eventually free itself. What's the best practice? Is there a software feature to leave some corners connected at first and then work them down last or what?

Say my clamps are 1" tall and I'm using a short mill on a piece of 1/8" aluminum. The collet will strike the clamps if it drops down far enough and gets near the sides. What's the best way to address the problem? I could always put a block of wood underneath it to bring it higher up in the clamp, but say I'm engraving the surface. If the part's not precisely flat the engraving will be shallow on one side and deep on the other and wood is hardly flat. What practice would address this problem?

I see that many endmills are not good for plunging into metal. What are the limits of plunging? I mean I can do a pocket without a starter pilot hole, can't I? Is that plunging restriction only applicable when there's not much lateral movement, like less than half the width of the mill or something?

Is there a decent online tutorial for these basic questions?

Thanks,
Danny