Device Firmware Update mode is a little trickier to get into, but will often force a restore even when nothing else works.
If for some reason, Recovery Mode doesn't trigger to let you downgrade your iPhone from a beta or public release, you can also try putting your iPhone or iPad into DFU mode. Of course, you could also install IPSW file without iTunes but non-free third-party IPSW file installers like Tenorshare ReiBoot, a professional iOS data recovery tool that could help you easily restore your iPhone, iPad and iPod.
