Good questions.

1) the speed is decided by you - trim your plane for a comfortable cruising/flying speed. In pattern, it is not a requirement but we strive for constant-speed flight. Find a speed that gives you enough time between maneuvers but is fast enough that the plane is flying with authority - not fast, but fast enough that a pull or roll won't put the plane near a stall.

2) it is iterative. If you go through and end up changing your CG, you should go through the process again, as changing CG will affect almost everything.

Trimming takes a long time. I am still learning the art of properly trimming a plane - with the ARF I have, I am limited to what adjustments I can make so I have to modify the trim sheet/process to fit my plane.