Splunk Enterprise does not provide a means of downgrading to previous versions. If you need to revert to an older Splunk release, just reinstall it.
Hope that helps ...
I 've already done for the quiter of 6.1.4 with a 6.1.1 using a .rpm package and it works corectly
If you are using a package manager, such as RPM,
Mr neelamssantosh do like the show in his commentary for it is very correct .
rpm -Uvh --oldpackage filename