All versions can be downgraded (via ctrtransfer) given arm9 access, which is easy to obtain on 11.3 and less
All versions up to 10.7 can also be downgraded, given arm11 access, by deleting system titles and reinstalling older versions (using sysupdater for example)
Of course you'd need to obtain a ctrtransfer image or a cia pack for the version you want to end up on, although both are widespread for 9.2
Note however that in your case you don't actually need to downgrade, exactly since all versions 11.3 and lower have an arm9 exploit