1. MariaDB 10.1/2/3/5 are available from the command line from the SCL repos. For it to run you'd need to stop the built in MariaDB as they both bind to the same port. I am not sure what else needs to be done. It would be nice to have it integrated into ClearOS. See https://www.softwarecollections.org/en/scls/rhscl/rh-mariadb103/, but you don't have to do some of the stuff it mentions.
2. Difficult. It means moving your DNS to Cloudflare. We are not using Cloudflare for *.poweredbyclear.com domains. Does it not work now or is Cloudflare killing it by forcing http > https?
3. No idea what you mean.
4. So would I. I would attempt it but am scared of the risk of me getting it wrong without others to support. Also I am now time limited.
5. Pro's and Cons. You would be forced to much more frequent updates even if you use an LTS version. This has a knock on for the developers as well.
6. This is a problem with the RHEL/Centos/ClearOS line of Linux
7. Could be useful.