Downgrade WordPress is way more easily that you think, all you need is follow the steps.
- Install plugin WP Downgrade.
- Once installed, go to Settings of the WP Downgrade.
- Key in the Targeted Version Number and save changes. You may visit WP Releases for the exact version number.
- Go to Dashboard > Updates, and click Re-install now to continue the process of Downgrade WordPress.
- Continue with Update WordPress Database.
- That's all you need to Downgrade WordPress.