How do I get a 1995 honda 300ex unstuck from reverse?

Check if the selector don't have any issue ... it takes brute force otherwise.
If it is badly jammed you might need to consult a mechanic.

try putting blocks in front of front tires about 2 feet away push in clutch let it roll to a stop at blocks might free it

Solenoid? Low battery? I've had both cause similar symptoms.

Without putting a scanner on the vehicle, ANYONE is only guessing but here is my 2 cents worth...

There a many popping noises and it could be Engine but since you lost Reverse at the same time...

I would also say that you broke the SUN SHELL inside your 4T60E Transmission and you lost Reverse, Second and 4th gear...

Check clutch fluid, must be low. If not this, then do clutch adjustment.

Does it seem to be tempreture related. i had a cutomers vehicle for almost 2 weeks and it started everytime. The thing was it was inside the garage. Finally one day I had pulled it out into the sun and when i went to put it back in, at that point it didn't start. It was a Honda but don't remember the year but it was around a 1995 like yours. It eneded up being the PGMFI relay wich would cause the exact sysmtoms that you are talking about. I have found out since then that this is a common problem. Give that a shot. I hope this helps and good luck.

You can leave it overfilled - it won't do any harm. You'll just have ATF spilling out of the dipstick.

you have got some serious drivetrain issues but please inspect the cv axles to make sure there not getting hung up somewhere

reverse clutch went out rebuild transmission

not a frozen linkage....the cable could be stretched but you should be able to putit in a different gear and get reverse if that is the case..it my have messed up the transmission as well. take it to a shop and find out what they have to say