Hi. I did everything according to the instructions. I put the "SkinName.png" file in cachedImages/skins, but instead of the skin that I installed, there are random skins that I have never installed before (some man in a raincoat, some typical woman from the 2015 letsplays, etc.). Im playing on 1.16.5 ForgeOptifine through TLauncher.

How can i fix it?

A friend of mine had a similar issue (no skin showing in multiplayer on his end), but using sklauncher. With a valid username and such. But he's in 1.20.6 (Fabric).

It doesnt work in every way Even if i delete every other mods

Just stop using shit Tlauncher, it has own mod for skins (YES ITS SHIT LAUNCHER INSTALL IT IN EVERY MINECRAFT INSTANCE), and this mod breaks OfflineSkins work

Make sure the filename matches your username, and I think TLauncher is also modifying skins, so you probably need to disable that.

Nah
Still doesnt work

Then... probably some other mods are incompatible? I'm not sure. Does it work with only this mod?

It doesnt work in every way
Even if i delete every other mods

I have no clues then... you are on your own, sorry.
It works on my end with Optifine and Forge, in 1.16.5 through CurseForge launcher.