LCabin

You can do real hardcore mode pretty easily with command blocks. It take only a couple to modify mob behavior and spawn rates but the main idea is just to have a command block set up that puts you into spectator mode when you die so you don't have to ban yourself from your own world. It really sucks that you can't really set the gamemode to hardcore on minehut unless you are doing a previously generated world(adding in a world into your server doesn't work very well, this is only through my own personal experience though). Obviously you could just go back into survival mode and pretend nothing happened but you can do that in single player too so if you're going to do that then you are defeating the purpose of the gamemode entirely.

MOTD stands for message of the day. In order to enable whitelisting on your server, all you need to do is /whitelist on. From there, you should do /whitelist add (username) in order to add accounts onto the whitelist.

Vanilla Entities as for as items go, only despawn if you have the chunks loaded in. If you are in the chunks that the items are in, you do indeed have a 5 minute timer to grab your items. This time can vary depending on the tps on the server as lag (especially on minehut) has been able to extend this time to about 15 minutes(at least in my own experience).

You need to give more information. You should make a support ticket on the minehut website.

Just try restarting your server every time you try to reset the world or set a specific seed for the world. Works every time for me.

You should always make backups or have a backup plugin lol Anyway there should be a backup tab in the server dasboard anyways. Try loading your latest backup next time so you don't have to deal with it again.