1997 ford contour.
I have a missing R2 relay in the aux. box under the hood.
Any clues on what this is for?

I do have electrical issues. The dome light, radio & power mirrors do not work as well as the rear defroster. Would this be due to the missing R2 relay?

Ford normally lays these out in the Owner's Manual, if you have one.

Typical Ford underhood relays are: Starter Motor Relay, Low Speed Fan Relay, Wiper Speed Relay, Wiper Park Relay, Fuel Pump Relay, High Speed Fan Relay, and A/C Clutch Relay.

My guess would be Low Speed Fan Relay.

Test all underdash and underhood fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145

Remove and clean contacts of any fuse that fails with steel wool or abrassive cloth. Afterwards, apply a thin coat of dielectric grease to the contacts. I would also carefully remove each relay, clean contacts with abrassive cloth, and apply a light coat of dielectric grease.

Remove and service one fuse or relay at a time, in order not to screw things up.