txbredred on "Main Index Template"

When creating a posts page for a blog the options for Template under Page Attributes are the Default, Front Page, and Full Width Page Template, No Sidebar.

For my blog page I selected Default. I want to move some elements on my Blog page, specifically the Leave Reply to the bottom of the post, but above the Share buttons (Jetpack Plugin: Sharedaddy)and I am trying to find the specific files I need to modify to do this.

Is the Main Index Template php file for the file/code for the Default template?

Also I have this question I posted last week and never received answer. Can someone help with this as well?

Theme: 2012
My Blog Page