My old P2 had a startup sequence of a short scale and then 3 ending beeps. I lust bought a used P2Vision and upon startup I get the small scale but no ending beeps.
If your motors are 2312 motors ( 2.1 esc ) If it goes ( deedle, deedle, deedle, dee, beep, beep, beep, beep ) its version 2.0. If it is missing last 4 ( BEEPS ) than version 2.1.
The same motherboard is used in all Phantom models whether it's a non-vision, vision, v2.0 or a v2.1. The difference Is in what equipment is added like wifi module, camera/gimbal, and 5.8GHz receiver on a vision plus vs a non-vision.