How many nrf24l01+ can be transfer data between themself in one pipe
I've written a lot of low level nRF51 and nRF52 code, and nRF24L01+ isn't that different. You can transmit instructions to a pipe address (e.g. 0x123456) and anyone listening on that address will receive the message. If you transmit a response back to pipe address 0x123456 then everyone (not just the master) will hear it. As long as your software can correctly ignore response messages then this will work.

While this defeats the purpose of the hardware filtering that using different pipe addresses provides, there's nothing wrong with it.