Planning ahead tends to work well when it comes to complex things like computers.
And beyond the obvious miscue, clearly stated by Microsoft, what possessed you not to make backups before upgrading your operating system?
Running a pre-release operating system and/or upgrading an operating system and risking all your files and applications without a backup is very much along the lines of "hold my beer and watch this!" I'm sorry if that
seems blunt but it's simple truth.
May I respectfully suggest that this has been a good life lesson. And now, before you get too depressed, have a look in the files and subfolders in the C:\Windows.old
folder. You might find good things there. But be warned:
Some of the contents of that folder are going to go away on their own soon - believe it.
BACK IT UP NOW!!
From now on, think ahead, read instructions, and make backups. If you're not sure of something, before leaping into the darkness ask questions of those who know. Clearly you figured out how to ask here in the forum after the
fact. Next time perhaps you'll learn something important before it's too late.
Best of luck moving forward.