Unless I missed that feature, no, you only have one version.
But it creates a link to archive.org so you can see if there’s older versions there.

You have two things, the application and the libraries.
The libraries are files with the data you want to host (wikipedia, stack overflow, etc).
There’s a lot of applications for different platforms. Some allow to download the libraries directly, otherwise you can download them manually into a folder and tell the app where to find them.

Yes! It saves it as HTML, readable HTML, PDF and image.
Results can vary a lot depending on how the page is implemented. Sometimes most of the formats are empty or broken, but I always got at least one that’s usable.

The official website has a lot of good resources. You can burn the firmware into the devices directly from there.

I have Kiwix (offline versions of Wikipedia and other online resources) and Linkwarden (preserve specific websites in multiple formats) running on my home server.