Viewing Revisions
The Revisions screen shows any backup copies of your post or page. Each time you save a draft manually or select Update, a revision is saved. Revisions allow you to look back at the recent changes you’ve made and revert to an earlier version if necessary.

WordPress.com will store the last 25 revisions for each post or page on your site if you have a free site (or our legacy Personal or Premium plan.) For sites on the Pro plan (or legacy Business or eCommerce plans), the last 100 revisions are stored.

To restore an earlier version of a page or post:

Go to Pages (or Posts)
Edit the page or post you want to view revisions for.
On the right side, under Page/ Post Settings, look for Revisions.