2 Electrical wireing questions

We have a 1980 international and are doing a remodel. Today I took the medicine cabinet off the wall in the bathroom and there is a hole about the size of a quarter that has several wires in it.
Yellow with nothing hooked to it that seems to be a hot wire
White with nothing hooked to it that seems to be a ground wire
2 smaller blue with a white stripe that are hooked to the furnace thermostat

A Red,Green,Brown, and Purple wire that are just cut off, and sticking out.
Does anyone know what the cut off wires are for or where they are supposed to go?

Second Question, We are installing a gas/electric refrigerator, it came with a small electric only frig.
Behind the frig is a Yellow wire and a White wire. I believe the White wire is a ground.
There is no juice to the Yellow wire though.
Can anyone tell me how to trace the Yellow wire to see where the problem might be or where to find the other end of it so I could test and see if it will carry current, and what and maby where is it supposed to start, and get it's juice.

Thanks for any advise , from 30+ years in a truck I know what a pain electrical can be.
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