To boot up your iPhone when you’re stuck in recovery mode, use these commands after you’ve install both iRecovery and libusb. You need both for this to work. Open up terminal and type the following.

iRecovery -s

printenv

setenv auto-boot true

saveenv

reboot

Now your iPhone should turn on. If it doesn’t then you may need to restore, or have a tethered Jailbreak. If you have a tethered Jailbreak, run Blackra1n, or redsn0w (just boot tethered now), to turn it on. If that doesn’t work, keep researching or send me an E-mail here.