You need to look at the monotribe 2.1 pdf to see which ring is unused
I think tip is , next ring isn’t and ring closest to ground is
The cable has three signals with a common ground
Two are needed and the earth from both should be connected to trs ground
If. You’d rather have tip as gate or ring as gate then you need to wire appropriately, depending on whether you wish to follow any protocol, but either will work as a4 can be configured
If the cable is three strands in a flat arrangement, it is likely that the central one is redundant
But you can test all connectors before cutting with an adaptor or easier still with a voltmeter