Why local version and container version is not same?

[rodphoenix]

I install CentOS-7-x86_64-Everything-2009.iso, and I look centos version,like follows:
#cat /etc/redhat- release
CentOS Linux release 7.9.2009 (Core)

Then I create a container and enter it, then I look centos version
sh-4.4# cat /etc/redhat- release
CentOS Linux release 8.4.2105

Why local centos version is 7.9.2009 and centos version is 8.4.2105 in container? If I want to change container version to 7.9.2009, how can I do? What detail command to use? Thanks

[TrevorH]

The whole point of containers is that you don't have to run the same thing as the host operating system. You've chosen to run a CentOS 8.4.2105 container - which by the way is massively out of date - the 2105 being 2021-05 so it's going on 3 years old and has had no security updates in all that time. You can't change that other than by choosing a different container.