We are in process of implementation of platform cipher to encrypt BLOB data, could you please clarify below questions.

1. Once keystore is activated and code is deployed onto the production if we observe any issues, can we rollback encrypted data on Prod and bring it on its previous state? how to deactivate keystore? 

2. Platform cipher does not consider existing data present into the DB for encryption, is there any better alternative to encrypt existing data once platform cipher is enabled?

Thank you in advance.