However, it MIGHT work in this case, as the database structure does not usually change within point releases. If you open up the 5.2.9 xml and edit the version you find in there to be the same as 5.2.6, then it will *probably* import ok.
But there's no way of knowing that and the only real answer is "test it with your own data"
Atlassian does not support JIRA downgrades. We strongly recommend that you do not attempt to downgrade the edition of your existing JIRA installation (i.e. from JIRA Professional or JIRA Enterprise to JIRA Standard, or from JIRA Enterprise to JIRA Professional), as it is a non-trivial process that requires significant manual intervention. If you still wish to downgrade the edition of your JIRA installation, please refer to the appropriate pages linked below.
Quote from this documentation: Downgrading JIRA
Hopefully it helps!
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