Using some specialized programs it is possible to transfer and restore older Whatsapp backup (*.db) and then use the chat backup function to generate a new backup, which currently uses CRYPT7 format. To get the previous CRYPT, you would have to downgrade it back with some CRYPT7 to CRYPT converter.
Convert WhatsApp Messenger message database to WhatsApp encrypted backup (original).
We have found 2 software records in our database eligible for .db to .crypt file format conversion.
Blackberry mobile phones and devices software - convert db to crypt on Blackberry
Cross-platform smartphone messenger also available for BlackBerry
Convert from db file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned db to crypt. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Windows Phone / Windows 10 Mobile software - convert db to crypt on Windows Phone
Instant messaging client for Windows Phone OS