I will be adding more information as I learn more. This is a summary of the knowledge on the subject I have gained so far.

Wayback machine

This is an obvious go-to website where you can see historic versions of sites. It is run by Internet Archive non-profit digital library.

https://archive.org/web/

Google cache

You can see cached version of sites in Google search by clicking the little down-arrow next to the URL.

Removed posts from reddit

Wayback machine most likely won’t snapshot the whole Reddit, so there is a service called Removeddit:

https://www.removeddit.com/

You can append the URL as it appeared originally on Reddit.