Make a support ticket and wait, next time save the server (/save-all) before leaving and get the download link (/dl world) after you've done a lot of work
Get essentials and a group managing plugin (pex, luckperms, etc.), that's kind of it if you really want vanilla. With those plugins you can add some essentials commands to default like /spawn or /sethome.
Go into server properties (in the panel), you'll find an option called level name, if you type in the uploaded world's name and restart the server it should make everyone spawn there.
This is a really easy game. Basically, someone comments a word and the member who comments under that makes up a word with the last letter of the previous word. For example: I make the word "Minehut" then the user after me makes up a word of their own, for example they make it "Time.'
Have fun!
The first word will be: Forums.