Woa!! You must use a wall mount bracket to do this. You just don't drill holes in the wall and then try to mount. Good wall mounts are not expensive (WalMart has a good supply of various sizes.) Here is a You Tube video with more information on wall mounting tvs.
https://www.youtube.com/watch?v=YdbWKDW4xa0
Try these: 0019; 0030; 0003; 0052; 0185
Also, most remotes have a seek and find mode where you just keep hitting the remote button until you find one thatn works. If you bought this at Best Buy, their GEEKSquad should also help free of charge.
I agree with the last answer failing power board. Most TVs have up to a three year warranty. However after this time if you are not familiar with replacing these boards which most people aren’t then it most likely would be cost prohibitive to have your tv repaired. However here’s a “ballpark” figure for a repair shop if you could find one. The replacement board approximately $190.00then roughly 2 hrs labor $180. And more than likely a diagnosit fee between $20.00 - $50.00.