You'll need JR, or JR compatible, receivers on the same channel as your transmitter. Technically you could move the one receiver from plane to plane but that would be a hassle if you wanted to fly multiple planes the same day.

When you change to "model number 2" or any other number (page 20 of the manual), it is a new model until you program it. That means all settings are at default values until you change them. Some transmitters allow you to copy settings from one model to another. The SX600 does not. It does have a data reset (page 19) that will set any model number back to default values so you can start over with programming.