Best practice for mysql administration?

Question

linux

Interested in best practices for a linux system administrator who somehow has to work with Mysql. Of course, there is a lot of information, I am gradually studying all this, but I would like to hear the experience of experienced people regarding the main points, namely:
1. What should a system administrator know in mysql, and what is the task of other specialists. Simply put - how deep do you need to be able to mysql?
2. What are the fundamental differences between mysql and mariadb? That is, what exactly should induce to install one or the other?
3. How is it easier to deal with all sorts of buffers, cache and other concepts, where is it written more clearly than on offsite? Optimized mysql in very small projects, but there is no understanding of how it all works.
4. Update from version to version. What is the correct course of action? On working servers, I updated everything 5 times, once very unsuccessfully, then I restored everything for a long time, etc.
5. Do you always need an update? On one popular IT resource they wrote that Mysql 5.7 is several times faster than 5.5
6. By what principle is the engine selected for a new table? In versions from 5.5 the default engine is InnoDB, but, for example, the user table, mysql database, has the Myisam engine...
7. Advise something else.
Thank you very much in advance!

Answer 1

1. There is a DBA - nothing. No DBA - everything.
2. Religion in the main.
3. Read the documentation. Sample.
4. Always backup before updating.
5. Compare yourself on loads typical for the selected project.
6. Start from tasks. It seems like MyISAM is faster for writing.
7. Google, mana and practice.