You set up Scrub and Snapshot tasks in the GUI. For Info how to do this step by step there is the official Truenas Documentation as well as countless youtube videos (Captn Stux, Lawrence Systems, SpaceRex,…). For email notifications you can use this very usefull script:
Yes, you can do that. You can add a new pool, add new vdevs to a pool, and even expand an existing vdev with new discs.
Pls explain…
It depends. Most likely no. Your primary read and write cache is your RAM. So adding more RAM is usually step number 1.
You can add as many users as you like and give them different permissions to your files. Again there are lots of step by step instructions found both in the official Truenas documentation as well as this forum and youtube.
You dont expose Truenas directly to the internet for that. Best way to do that is using Tailscale.
You can encrypt a dataset.
You can use an app like Nextcloud, or let him have access to your network with Tailscale.
But of course this has risks…
There are Plex, Jellyfin and Emby available in the app store. Truenas uses docker to run the apps.
You can try to enforce it, but it is not recommended.