You can find a good overview of the materials that can be cut here:

Yes, that works well! It is important to first check carefully whether it really is genuine leather or just artificial leather with PVC. PVC develops chlorine when lasered, which is a poisonous gas and must therefore not be lasered

Create the desired outlines as a vector in the program of your choice (preferably only lines, no areas). The file format .svg has proven itself and if it can be opened in Inkscape, this is usually a good sign