You are extremely close to reaching inactivity as you haven't been active since 01/01/2018. You will become inactive on April 1st if you do not contribute before then. If you are still inactive after April 1st, you will risk losing your Rollback rights.
Now, you have a rollback feature. The rollback button will be shown on the end of the revision. If you click the rollback button, the edits by a user are reverted to the revision to the last revision by another user. Unlike the 'undo' button, this button reverted the edits immediately.