Yes, you could shutdown, replace your flash drive with the old one and boot up with 9.10.2.
On occasion, users run into issues where "it used to work" before I upgraded and "now it doesn't" after they upgraded. If that's the case (and you haven't upgraded the pool), you can roll back to an older version and re-test the issue. If you upgrade the pool, you'll have to live with the current version and hope for a fix.
FreeNAS 11.0 was originally going to be called 9.10.3, back before the Corral snafu. Generally a switch from 9.10.2 to 9.10.3 wouldn't be considered major. But, given the change of the underlying FreeBSD version from 10.3 to 11.0, iXsystem decided to go back to the old naming scheme. I think the general consensus is that the upgrade from 9.10.x to 11.0 was uneventful. But, if I were in your shoes, I'd wait a minimum of a month or two before upgrading the pool.
i saved my config then did a new freenas install on a new stick and then uploaded my config so not sure if i could roll back anyway