How to create older Lightroom Classic 10.2 while still using v. 10.4?

Why?  I am getting this error message in Lightoom Classic 10.4 when trying to upload a web gallery -

FTP transfer failed with message ‘?:0: attempt to call field 'AgNetIO' (a nil value)’.

Thanks to the Adobe Support Communities I think I found the solution to the above error. 

Official Adobe Support expert did not know of this. 

The above problem does not exist in LrC v. 10.2.  I need a bit more information on creating an addtional-older- Lightroom Classic version 10.2. (This is a temporary solution until I upgrade soon to Catalina in the Mac OS) while continuing to use the Lightroom Classic v. 10.4.

I want to be sure I have my catalogue is still maintained in version 10.4.

THANK YOU!

Picchic