does it also work for multiplayer?

and can I just install it over my 3.13 version?

Yes it does work in MP. Need to be installed on all participating computers, of course

I am not sure i understand the second question. Its a suplementary patch for the version 3.13 of BTS. Is is supposed to be installed over 3.13.

I have patch 3.13 installed.

do I need to uninstall it or can i just install the Bhruic patch

I have patch 3.13 installed.

do I need to uninstall it or can i just install the Bhruic patch

You just install Bhuric's patch over your 3.13. No need to uninstall the official 3.13.

thanks for the info.