You can adjust it here

Settings shortcut: Comments > Comment body font

Not quite. From what I’ve read, I think only text is downloaded, pictures and other media are just links. So not everything needs to be downloaded. Also to trigger/maintain this connection (federation) at least one person from your instance needs to be subscribed.

But you won’t find this community in the search bar because you’re not federated yet. So to trigger the initial federation you’ll need to search for the full URL, the entire URL including “https://” (https://lemdro.id/c/android) It won’t show up at first, so try again in a few seconds, and sometimes you’ll need to try a lot of times if the instances are running slowly. But eventually your instance will find the other community on the other instance.

But at the time I’m writing this lemdro.id is apparently offline so it won’t work at all right now.