Will initiating recovery mode on an iPhone permanently disable it until it is recovered?
I had an extra iPhone (that didn't have important information) which I just tried it on. Simply initiating the recovery process (by pressing and hold home button while plugging it into the computer) will not cause anything irreversible to happen on the phone. You still have to click a few buttons on iTunes to start the process.

To go out of recovery mode, simply eject the iPhone through iTunes, disconnect the cable, and restart the phone. It will be in the exact same state it was previously.