Is it possible for GOG to give us access to the previous 2.0.119.430 (A) patch for the offline version of the game ?

The 2.0.119.430 CN has a bug which makes some tooltip information to disappear. The only way to revert to the previous patch is to use the GOG Galaxy version of the game.

Thank you.

Unfortunately GOG offers the downgrade option via Galaxy only.
Without using Galaxy, in order to rollback to a previous version you have to reinstall the game using an older version of the offline installer and this means you have to backup all the versions of the installer as they are released on the site.

That said, you may want to try asking the support to provide you the offline installer for the version you are looking for.