MySQLの以前のバージョンをyumでインストールする件

Download MySQL Yum Repository
https://dev.mysql.com/downloads/repo/yum/

今だと

The repository packages available below will provide MySQL Server 8.0 by default. Other versions can be obtained by editing the repo setup file installed by the package. See the Quick Guide to Using the MySQL Yum Repository for details.

とある。

A Quick Guide to Using the MySQL Yum Repository
https://dev.mysql.com/doc/mysql-yum-repo-quick-guide/en/