there are almost half as many cast ons as knitters in the world.
If you want to learn how to cast on, look in that section of the videos. There are several ones you can try.
to make small projects, it really does not matter all that much, which one you use.
of pretty edges, stretchy edges and so on... then it matters. But start knitting first, then worry about that.
so cast on any way you like, then go back to the video about the small project and work from "right after cast on". however the stitches got onto the needle there is really no matter.
and: no, for casting on (regularly) you do not cut your yarn. For none of your practice pieces as a beginner you do that - until you finish something and want to keep it. Then cut off, start the next thing.