Hey scotty, I have a 2001 toyota camry, 2.2 4cyl Engine with the 4 speed automatic transmission with over drive. Car has 90,250 miles on it, I accidentally shifted from drive to reverse, I did not hear any grinding, engine did not stall, the car still moves under its own power, transmission still shifts like normal, is the transmission still good? Did the gear change damage the transmission? if so what should I do for maintenance?
Some transmissions have the logic built in to not shift into reverse if the car is moving forward at more than a crawl. I don't know if yours is like that but it sounds like you got lucky.
Maybe it did, maybe it didn't. You will never know without disassembling the transmission. And there's nothing you can do about it now.
Hopefully it lasts.

