I think I saw this around four years ago for the first time... someone sent it to me on telegram, but in another language.

Not like this in Persian! Seperate is jodaa in Persian (جدا), and touch can be translated to tamaas (تماس).

I don't think so. I mean, even if an instance with an important community has a problem (e.g. goes offline) we can simply create that community on another instance, but as long as there are no problems I think it's better to have just one community.

Or download it from Google Play Store?

The Material Files repo shows the last update was three weeks ago, but the latest version on the releases page and f-droid are from 2022. This is confusing...

Aegis is great! I really don't know why people use Google Authenticator when much better alternatives exist.