Prop it with an 18 X 6 or 18 X 10. This is an engine that develops power at lower RPM in the 8000 to 9000 range.
It needs to be heavily primed to start well, a good shot of fuel in the carb helps a lot. Don't drown it, just a CC or so.
It will run well on no nitro fuel if you use a hot plug. OS "f" works well.
It will start by flipping in either direction but flipping it back against compression seems to work best. Use a chicken stick or glove, it doesn't kick back frequently but if it does, there is a lot of force. I hear claims of starting one by simply spinng the spinner. I don't dispute those claims but mine seem to like a good, strong backflip against compression.

The disk on the carb is, as you guessed, the idle adjustment. It is not like a needle style as it really controls the opening in a small slot. Very little movement is required to affect the adjustment.