ATtiny, RF24L01 transceiver and IO

[system]

Hello to this great forum.
Forgive me for my bad english.

I want to give me some advice for my project for home automation.
I want to setup a network in my house, with some boards, that each board communicate to a master board with RF24L01.

So if we have 3 rooms and name them AA,A1,A2
i want to have a uno board with a RF24L01 as a master in room AA
an ATtiny with RF24L01 in each other room.

1. The first thing i want to ask is what IO will be left for the ATtiny to communicate with relles or temperature sensors or some buttons to control same devices in this room.

2. Can i separate the data from room A1 and A2 to know the uno board where to send the data and from where the data is coming from? can i do this in the code? if every data from the A1 room have a letter A before everything and B from A2. Will be problem if A1 and A2 send data the same time?

Thanks for your time.

[system]

Thanks to Fritzing i made a diagram.
The second question was more significant

If i press the button S1 in room AA I will send a data to both other two rooms but the room A2 will ignore the data(because of the code) and the room A1 will turn on the LED1.

If i press the button S3 in room A1 I will send a data to both other two rooms but the room A2 will also ignore the data(because of the code) and the room AA will send an answer that only the room A1 will turn off the LED1.

and now the problem.
If I press both S3 and S4 buttons what will happen on the board in room AA.
Is there any way to realize the two data packets?
What if i have to add more boards in more rooms?