That is normally a hosting bug – use FTP to upload the theme and you should be fine
To put it very simply no ALL work MUST BE ORIGINAL and YOUR OWN not an EDITED VERSION of someone else’s file
Whatever is your style? to become a featured author you need to be something quite special and make a difference here – its not going to happen straight away. You need stand out files, sales, skills etc
You need to sign in using the account which purchased the file to get support from the author
So it is the same code? Of course it is not allowed.
No not the downloadable one as it cannot be redistributed. If you bought it you can use it in the demo but do not make it accessible to buyers
Not without permission from the author. You can buy it and use it in the preview but without a purchase you need permission. Either way you cannot include it in the end product i.e the download version not the preview as you cannot redistribute it
What do you mean “data”?
Your file needs to be your OWN design (not just rearranging someone else’s) and most importantly your OWN code
Release a few files, generate sales, get noticed
It depends how you set it up but imagine you have a site which is like here and people pay either a % of sale sor a fee to be a member – that would require an extended license (multiple paid for users in the end product). It can get a bit complicated in some cases but look below the price of that WP theme in the item page it says “Use, by you or one client, in a single end product which end users are not charged for Details | Licensing help“
So you would be charging people to use it hence the need for an extended license.
Obviously this is several thousand dollars so you might do better to speak to the author and get a cusotm job done to closer to exactly what yo want but based on the framework