Car is squealing persistently from rear right tire

If in fact they are doing it sometimes, but not all the time, this is indicating worn out belts, and they need replacement.
Belts can look good, but can slip and squeal when they get hard and brittle.
I, too, have had that experience with my Hondas.
If the belts did it all the time, you would look for a defect in of the components that the belt is driving. ( Water pump, a/c compressor, idler pulley, power steering pump, alternator, etc.)
God bless your efforts.

Check back all parts to attach to wheel could be broken and body must be something broken or loose.

CHECK AIR PRESSURE ALL TIRES

Jack up car by right rear wheel under control arm or axle, so its off the ground. Grab tire at 3 oclock & 9 oclock see if there is play back & forth. If play most likely wheel bearing is bad & needs to be replaced. While your there, grab tire at 6 oclock & 12 oclock, see if there is play moving in & out. If so see what suspension part is worn.

is the right rear turn signal doing the same if so it may be the turn signal switch

With your hands, press down on the seat cushion where it meets the seat back. Locate the retaining bolt(s). Some models retain the seat with one bolt in the center; others use two, evenly spaced left and right.
Remove the retaining bolt(s).
Life the back (toward the rear of the car) of the seat bottom upwards while rotating it toward the front of the car.
Disconnect the hooks at the front edge (during the rolling motion) of the seat and remove the seat bottom.
Remove the carpet (in the luggage compartment) from the rear of the seat backs.
Remove the seat back mounting bolts from the luggage compartment side.
Lift out the seat back.
If the rear side bolsters or pads are to be removed, remove the lower mounting bolt, then push upward to free the hooks.
Hope this helps you.

Below is the wiring setup for your car:

1990-93 Honda Accord Stereo Wiring
Constant 12V+ White/Yellow Switched 12V+ Yellow/Red Ground Black Illumination Red/Black Dimmer n/a Antenna Trigger Yellow/White Antenna Left Rear Front Speakers 6 1/2" Doors Left Front (+) Blue/Green Left Front (-) Gray/Black Right Front (+) Red/Green Right Front (-) Brown/Black Rear Speakers 6 1/2" Rear Deck Left Rear (+) Blue/Yellow Left Rear (-) Gray/White Right Rear (+) Red/Yellow Right Rear (-) Brown/White Best of luck,
Greg

check the brake, hand brake cable, differentail, driver train. in that order.

Radio Constant 12V+: Blue/White
Radio Switched 12V+: Yellow/Red
Radio Ground: Black
Radio Illumination: Red/Black
Radio Dimmer: n/a
Radio Antenna: Driver’s Pillar
Front Speakers Size and Locations: 5 1/4′ Doors
Left Front (+): Blue/Green
Left Front (-): Gray/Black
Right Front (+): Red/Green
Right Front (-): Brown/Black
Rear Speakers Size and Locations: 6 1/2′ Side Panels
Left Rear (+): Blue/Yellow
Left Rear (-): Gray/White
Right Rear (+): Red/Yellow
Right Rear (-): Brown/White

Your rear brake pads are most likely worn to the wear indicator which can make a high pitch squealing noise. It is very common that it will squeal when backing up, but not when applying the brakes. 50,000 miles is about the average life for rear brake pads on your car.