multiple failures are very rarely (never) a relay fault. you almost certainly have a short somewhere.
that is why i asked you to try with the boot open, if the boot contained the short you'd find everything else worked when the boot was isolated.
what you need to do now is the fuse removal method to identify the faulty circuit (same method used when diagnosing a house using circuit breakers)
we know the failed circuits are:
electric windows
side mirrors
back fog lights
rear window heater
if you can find no other failed circuits, you now know one of the above 4 circuits is causing the fault.
so try removing the fuse for each of the 4 seperately, when you reomve the fuse for one of the circuits everything else should start working again.
the fuse that is reomved when everything works is the fuse for the circuit that has the short.
do this test and let me know which cirucit is faulty, then we can decide how you should identify and repair the fault.