After successfully executing this query, how do go I back to the previous stage in MySQL?
If your table engine is not InnoDB, or you haven't used transactions for this operation, then it might be not possible.

To have possibility to ROLLBACK DML statements (like INSERT, UPDATE or DELETE queries) you should use transaction blocks:

START TRANSACTION;

UPDATE CUSTOMERS SET ADDRESS = 'Pune' WHERE ID = 6;
-- and more DML queries

COMMIT; -- or ROLLBACK;


Since transaction was COMMITed it can not be rolled back. Only option (that I see) is to restore database backup (if it exists).



UPDv1:

Just as an advice: Before you do any critical changes to database (perform transactions, execute complex scripts, that includes INSERTs, UPDATEs and DELETEs or change data structures with ALTERs or DROPs) make a backup of your database.

You may probably restore backup as another database copy, then test script on it. If nothing goes wrong, then perform script for a real database.