Car trouble’s a pain, especially when it’s reverse gear that’s gone AWOL. I’ve had a similar issue, but with my mobile gaming luck, it was ‘3 Patti Gold’ that froze up. The app wouldn’t let me skip or deal cards in reverse order, just like your car refusing to budge https://the3pattigold.com.pk/ . I had to force close and reinstall. As for your car, I’d suggest checking the reverse clutch pack or valve body, as you suspected. It’s not cheap, but it’s better than replacing the whole transmission. Good luck!