To get a Kiosk to Retail you need the unlock code. And to jailbreak a console it has to be 3.55 to or lower and to downgrade you must have a retail and a Flasher (buy not E3 the quality of these are horrible)
So you need:
1. Unlock code
2. Soldering skill & Flasher
Here in the forum we have guides and service on how to solder and downgrade
^^ this is wrong information, i've never had a problem with any e3 flasher infact i think that they are great its just that people don't install them correctly.. assuming that your console has a nor chip cause if your console has nand you will need to solder progskeet device.
also you don't need any unlock code, just flash the chip with 3.55 coreOS put the console into factory service mode and downgrade to the e3 retail custom firmware. your console will now be on converted from kiosk back to retail.
you must downgrade back to 3.55 to convert the console to retail because 4.11 has new pup update security checks and you will just get a corrupt data error message unless your on firmware 3.55