[Galaxy S II Q&A, Help & Troubleshooting] neobirdrio:
Boot loop? Stuck on boot screen??

For newbie : Solve your bootloop or freeze problem.

Due to those related problems, Dont make it a hard way, it can be solve with just a simple step.. normally this happened after flashing something new to you phone, with odin or cwm..then the phone wont boot up, you stuck on the boot screen such it keep repeating or freeze on samsung image. For those who new to flash, or your hand itchy to try flashing, please make sure you know well what you are doing. To flash new custom rom, i prefer your phone has been rooted.. then, your battery life must be at least 40%..the more is better.. 70%+ battery life for better confidence. If your phone running out of battery during flashing... you are in worst case scenario then.

Oke now you going to flash new rom.. before that, make sure you full wipe, even sometime dev said no need to full wipe, for safety reason, full wipe, i hardly press this step especially for those who new to flashing, especially for those who from Samsung stock rom to flash custom rom like Cyanogenmod , MIUI , Checkrom , DarkyRom..etc. and its recommended for those who try to jump from custom rom to other custom rom.

1 - For those who now already in trouble, i prefer you to start all over again from by completely refreshing device back to normal, the most stable stock firmware by region so far is I9100XXKI3 2.3.5. Download the complete files here with a complete guide. make it done.

2 -Rooting your phone can be done by following the guide here. You can use hellcat to root, but as i said, this is for who new to flashing. make rooting done!!

3 - Flashing new rom, before that, do this, after you done rooting your phone, boot up, get into Setting > Application > Development > USB debugging mode "ON"... in some cases this is not necessary but i prefer you do it. Now you can flash new rom.. are you nervous?? put that away, just relax and calm. it just your phone, not your soul :) .

4 - Lets say you going to flash MIUI ( example ), normally MIUI rom file in .zip. So you need to flash it in recovery mode. Move the .zip file into your sdcard.. prefer not your externel sdcard. Turn off, boot into recovery mode by press and hold down Vol Up + Center Button + Power button together at the same time till you'll see you get into recovery mode. Check you CWM version of top of the screen. If your device running recovery 3e.. you will lack some options and functions. You need recovery v4 or later, you can get from here. Or from your phone, get into Android market, download RomManager app, install then open it, and tab flash recovery mode, select your phone model, then it will download and flash the recovery mode v4 which give you useful options in recovery mode.

5 - Through recovery mode, wipe data/factory reset, wipe cache partition, then select advance then wipe dalvik cache. DO NOT REBOOT!! Go back to 1st menu page, select INSTALL FROM SD CARD then select the downloaded rom zip file in the folder, then flash it.. now keep your eyes open when it flashing, dont blink even once :) .. you'll see it will prompt you something like this, " installing from sdcard succeed" when your device successfully install the rom. That mean you're done flashing your new rom. Then select reboot the phone. This time you gonna feel like getting an heart attack.. Your phone reboot and samsung logo appeared and after few minutes waiting, its still there, you stuck there.. dont cry or smash your phone. Are you going to restore back to stock rom and start all over again?? no need!! Since just now you succeed flashing new rom rite? Dont forget, now you phone running MIUI, not stock or previous rom anymore, but it just wont boot up.. in this case, it is important to know what custom kernel work good for your custom rom.. If MIUI rom, siyah or fluxi work good, Siyah kernel can be download here. Fluxi kernel can be download here.

6 - Fixing boot up problem, some cases you can't access recovery mode, btw, recovery mode cant help you fix this, sometime it have problem mounting sdcard. Now, shut down your device, or simply remove the battery then attach it back, boot into download mode, use Odin 1.85 to flash the match kernel. Then you phone will successfully boot up and get into your homescreen like normal. Just flash compatible kernel will solve boot loop or stuck problem. If you still stuck on boot, try another version of the kernel, or change the kernel. keep flashing the different kernel untill your phone get rid of boot problem.

7 - If you dont like siyah or custom kernel, you want to use MIUI stock kernel, just simply flash the rom in recovery mode again and this time it will work without boot loop or get stuck. Your phone will run MIUI with its pre-installed kernel.

This guide made for those who new to fashing and faced a problem at boot up..This is safe method in order to recover back your damaged phone from any failure you made. Hope you manage to get it clearly. If you do from the 1st step, 100% your phone will not getting any problem. But if you still do have problem, inbox me or add me nexsentinel@gmail.com on facebook or G+ for real time help.