Browsing a full disk image

Hi

This has to be a common problem, but maybe I can't find prior examples because I'm using different language! 😝

I have a disk image (.dmg) on an external hard drive that I want to browse. It is an entire drive of some 220GB which I created using diskutil, after a HDD corruption. My TimeMachine backup isn't as recent, so having restored from Time Machine my task is to fill in the gaps from the .dmg. Note, I couldn't restore from the .dmg itself as for some reason it made the new drive non-bootable (most likely the image copied the corruption and - guess what - the corrupted HDD wasn't bootable. All good fun! 😉).

Two questions therefore:

1. How do I browse the .dmg? I believe that like all .dmg files, if I double click it expands out to occupy new storage (like a zip file) - and you get no option as to where the files are deposited. On the disk it occupies, there is no space for this operation.
2. How do I carry out (potentially automate) the task of filling in most recent files - and not just for my account but for the other Mac user accounts?

Many thanks

Matt