Are these updates possible?

Hi!

I'm superhappy with what I've achieved with my site https://www.continuityguide.net/. But I do wish to elevate it for my users. So I wonder, are these things I list below possible to do on Squarespace?

Check boxes - I'd love it if my users can put a mark when they have finished reading an arc. I'd like to have a little box that they can check when they're done. This might demand a log-in. Is it possible for me to have log-ins for my users?

Comments - It would also be great if I could have a comment section below each arc that is foldable. So that it says like:
----------------- 23 comments ---------------- and when you click on that row it revealse the comments and a comment box where you can write yourself.

Pop-up preview of a site - I'd love it if it was possible to have a preview minitature of a website pop-up when the user hovers the arrow over a link. Or press on the link without release.

Are stuff like this possible on Squarespace, or is the system to rigid?

All the best!
//Tommy