Xbee configuration

I want to create a network of 12 Xbee clients and 1 server that gets all information from all of them. What I understood I have to put a "router" in the middle to split in two the network, 1 server -> 1 router -> 6 xbee -> 1 router -> 6 xbee Am I wrong?

Also I would like to send the result of one pin that is going to be 0 or 1 ( push button ). When these devices are sending these information, there is a way to detect which was the client? Like client number 1 sent HIGH, client number 2 sent LOW, etc...

I did some research and I understood that sending the HIGH and LOW is possible but I just need these two clarification :)

What I understood I have to put a "router" in the middle to split in two the network,

Based on what? A router is useful if two points that need to communicate are too far apart.

When these devices are sending these information, there is a way to detect which was the client?

In AT mode, not unless the sender sends something that defines who the message is from. In API mode, yes.