How do I get back to my original website? Template is different now

Hello! I made a squarespace site about 10 years ago. Long story short, in the last few years I attempted to do an upgrade. I was experimenting with some different templates. Basically I only got so far with it, and gave up.

Tonight I logged back in, and when I click my "current site, it goes directly to where the new template is. And I can't access the old one to do some minor tweaks to it. 2 questions:

1) Does anyone here know how I can get back to the original site so I can make some simple tweaks to it for now?

2) I'd like to keep the more updated template, and continue to work on it while the old template is still live on the web. Is there a way I can do that, while in the meantime get back the old template and be able to do some simple updates to it?

Thank you in advance!