Retrieving an OLD whatsapp back up from google drive
You can't access raw files of WhatsApp from Google Drive (it is a hidden folder), and you can't choose which version you want to restore from (I cannot even see versions at my account).

But, you can try to restore the last backup from Google Drive, and then manipulate 
WhatsApp db files in order to delete some of your messages.
There are plenty of guides out there on how to decrypt WhatsApp db, after you decrypt it, delete the non-relevant messages and put the db back in your sd, Didn't try but it might works.