Help How to downgrade from v4.0.4 to v2.3.6?

[nephelae]

I don't hate the upgrade but I've had lots of troubles like the screenshot and the battery is draining so fast and some apps force close so often. And if I downgrade my phone will it be safe, I mean it won't be bricked, right? Thanks so much for helping

edit:
here is my build info?

i9100ZSLPQ

 

[SCPadgeebar]

May I ask, did you do a factory reset after the upgrade?
If not, then press and hold these 3 buttons at the same time, Vol Up+Home+Power. You will be taken to the 3e Recovery and navigate to factory reset by pressing the down button and select it using the power button.

 

[lunatic59]

Downgrading involves rooting and flashing an original stock rom. A factory reset is a much better idea. When a phone is updated without the factory reset there are a lot of possibly incompatible remnants from the old version hanging around that can and do cause problems. Do the factory reset and if that doesn't fix it for you, then we can give a step by step to downgrade, but at that point you might just consider flashing a Jelly Bean rom. Why move backwards when you can move forward?

 

[SCPadgeebar]

Actually downgrading does not need root access. Get the appropriate stock Gingerbread Rom for you S2 and flash it via Odin.