How to use D Debra Audio AU400 Pro UHF 4 Channel Wireless Microphone System

At :43 in this video, it shows a connection to speakers. Will this transmit all four microphone inputs or just the microphone for that connection?

is this can be used as internal communication as a phone?

I bought 3 sets of the 4 mics which equals to 12 mic’s in total for a choir. The problem is they are not independent channels to the receiver, they hop on all 3! How do I solve this?

How do i connect the microphones to my Macbook?

In other words I have to use four tubes to connect the mixer with the ones of the mics.
Correct? Or do I only need one connection (mixer to microphone mixer)