old

[Michał Ratyna]

How to change the new Jira for the old one?

It was much better

[Nic Brough -Adaptavist-]

If you are on a Server version, then you can use any version of Jira you want, that was released before the end of your licence.  But be aware that you can not downgrade your data - if you do decide to go back, you will want to re-start with an empty Jira (and probably import some of the data via CSV)

If you are on Cloud Jira, you can't go back.