You need to:
1. Get Trucha Bug Restorer
2. Run TBR, press B and choose downgrade IOS15
3. Run TBR again, choose IOS15 and go to IOS36 menu->Downgrade IOS36
4. Run TBR for the last time, choose IOS36 and choose restore IOS15
5. Then you have to run AnyTitle Deleter and delete IOS249, 222, 223, 202, 250 and 254. If any of them are missing don't worry about it, I don't remember exactly which IOSes the 4.2 update stubs.
6. Afterwards, you can reinstall cIOS rev14 choosing to use IOS36 for the installation.
Note: HBC might have been deleted if you didn't update to the latest one, if so you'll have to use bannerbomb 2.0 to run Hackmii Installer and reinstall HBC.