Q: Car not reversing, but going into forward.

Hello, the transmission your car is equipped with has a dedicated band that locks up to one of the drums to make the trans rotate in reverse. This band is only applied in reverse and manual low (putting the shifter in gear 1). Reverse is a mechanical gear and has no solenoids involved. The hydraulic fluid is applied to a piston inside, that is connected to one end of the band. Fluid fills the chamber where the piston is located and applies pressure to the band. The band has pressure on one side and locks on the other tightening around the drum causing the gear to rotate in a reverse direction. There is the possibility that the piston has an internal leak, letting fluids bypass the piston and not engaging reverse. It is possible the rod between the piston and band fell out or the band is broken. You may need to enlist the aid of a mechanic to do an inspection of your gears. It may be necessary to have the trans removed to repair the band.