Does the wishbone bus used in the caravel soc follows the B4 version of the protocol or or is it some other version?

good question, I don't think it follows a standard. It is the most basic version. Best bet is to check the code. As the SoC is now done with litex, you might be able to find details about wishbone litex support: https://github.com/enjoy-digital/litex/blob/master/litex/soc/interconnect/wishbone.py