Best practise for editing the registration page before final submit

I have registration page divided into 3 pages

After each page, we save the Data to Database and at last page, we have option to edit the data which user entered in all 3 pages.

So what is the best practice to edit the data in this case?

I have couple of questions?

1. should I check whether each fields in page was edited and update the same in DB.
2. What if there is error while updating the Data, how to restore the previous state?

Please suggest some design pattern of good approach for achieving the same