by rotating the potentiometer you would switch between "record start position", "record stop position", "replay movement" and "erase positions".
For your first project, do yourself a favor. Use the switches that come in the parts kit. Yes, you could use a pot this way, but it does not include a push button capability, as you implied, so getting from "replay movement" back to "record start position" will involve going through "record stop position". The stop position will be recorded many times while you're fiddling with the pot.