MYSQL Patching -Roll back
You can have 2 strategies:


Stop MySQL Server and backup (just copy all files to some location) - folder c:/ProgramData/MySQL/data
Make a full dump of all databases 
mysqldump -u root -p --all-databases > c:/backups/all_db.sql


p1 - if You plan rollback exactly for 5.6.30, 

p2 - if You plan go till the win, best to have both.

then You must have old installer for revert back at any time, You can download it from official archive - https://downloads.mysql.com/archives/community/

Then You if You decide revert back:


Uninstall latest MySQL - by windows tools
Install 5.6.30 from previous step
Copy folder c:/ProgramData/Mysql/data saved on previous step
Start MySQL


If You also make a sql dump - You can use normal restore procedure

mysql -u root -p &lt; c:/backups/all_db.sql


, but it work much slower than simple file copy.