Yes! Previous ESCs will work with it. LEDs on that are controlled directly by NAZA.Juat take care of the CW and CCW ESC and motorsI still have the P1.1.1 ESC's, but I guess they should just work with the P2 board, right?
Yeah, the Zenmuse should get power from the board. But with the first board I tried, it did not get the power. I got the drone 2nd hand, so I don't know if it was a factory issue or if the previous owner wrecked it. That's why I put the new upgrade board in. That was last June, didn't know the V3 came out a few weeks later... bummer...
I have the same cable for my existing setup, but without the iOSD lead. I think I'll upgrade to this lead, it worked flawlessy.
(CW and CCW motors are wired differently, do note down before taking them apart. A good idea will be to take pictures before taking everything apart and match with the rotation signs as mentioned on the P2 shell)
On v2.1 ESCs, LEDs are controlled by the board, thats why they have those ports.(I still got those LEDs to work with a coded PIC mimicking the signals they would get from the P2 board)