MAGIT: How to show 2 side-by-side window of only changes, not whole document

Question

Once in the Magit buffer, hit E, choose the diff and when they're displayed then switch to vertical mode with |.

So far so good.

However, this shows three panes, not two.

1. How to show just current and last commit?
2. How to make both document linked while scrolling? At the moment one of them can have collapsed headings while the other does not, and it's impossible to see.
3. How to only show changes (not all document) like in Github, for instance, where it only shows changes and some lines before and after?

Thank you!