How do I bring up the turbo tax version that I worked on before I filed? I need to look at the section about Mortgage insurance deduction in the online working copy.

To go back into the return, you can use the Amend option (without really amending). Here's how:

From Tax Home, select Amend and then use menu on the left side to go to the Federal tab, then go to Deductions & Credits, and scroll down to Your Home to access the mortgage insurance deduction section of the program.

If you accidentally start to amend, here's how to "un"amend:

https://ttlc.intuit.com/replies/4170678