Bookmark those. Those pages are from the 2016 Arduino MAIN Site, back when they were way easier to find basics in. I got there using The Wayback Machine, a web archive.
Foundations and Hacking contain tons of stock Answers.
These links are to archives of the Arduino website made by the Wayback Machine.
The Internet Archive organization that created and maintains Wayback Machine is very dedicated to preservation of knowledge. This is a well established organization with significant resources. Wayback Machine and other projects of the Internet Archive organization are very popular, so there is a tremendous amount of momentum to keep the organization and their projects operational into the foreseeable future.
So I think that you can have reasonable confidence that once web pages like this are archived by the Wayback Machine, they will remain available from Wayback Machine. However, unfortunately Wayback Machine is subject to periodic outages. So it is entirely possible that you might find that a page is temporarily unavailable.
If there is some information feel is very important for you to always have access to, by all means make a copy of it. You are also free to redistribute the Arduino documentation content under the terms of the Creative Commons BY-SA 4.0 license: