Change Minecraft ingame skin?

I'm looking for a Minecrfat mod in version 1.12.2 with which I can change my skin ingame. So, so to speak, that I can enter a username and then get the skin from him

In addition, a mod would be good with which I can change my complete identity. So name in chat and such

You still have to re-enter the server so that the skin is visible.

I only know the identity function from hacked clients. However, this is only intended for streaming or recording. So the name doesn't change for others. That is not even possible.