Update Samsung Galaxy S3 I9300 to CM10 Alpha Unofficial Jelly Bean 4.1

The CyanogenMod 10 is based on the Android 4.1.1 Jelly Bean and now a preview build has been created by an XDA forum member and developer. This article teaches you how to successfully flash the Jelly Bean CM10 ROM on your Galaxy S3 I9300 phone. Make sure to read the entire tutorial and don’t think about skipping any steps as you might end up bricking the device.
This guide should be used by advanced Android users and please note that this build of CM10 is only an alpha version and it shouldn’t be used as a daily ROM. Use this ROM only for testing purposes so that you’ll get a taste of the Jelly Bean features edited by the CyanogenMod team. Also, note that not all default CyanogenMod settings and features were included in this release and you shouldn’t expect any major changes from ICS. The FM Radio, Camera, Wi-FI aren’t fully integrated and might not work correctly.
Before moving to the tutorial guide, you should read the pre-requisites info below. That’s how you will learn what steps you need to take so that you’ll manage to flash Android 4.1 Jelly Bean CM10 Alpha build on your I9300 device. Here’s what you need to know:

• Apply this ROM only on the Samsung Galaxy S3 I9300. Do not attempt to flash the ROM on US models of Galaxy S3.
• Backup all the important data files stored on your device. This step is required because the tutorial features a step that will tell you to wipe the phone data. The files you wish to salvage should be moved on the device’s internal or external sdcard.
• To backup applications, SMS, Call Logs and APN Settings you will need to use the following Android tools: AppBAK for Android apps backups | SMS backup & restore | Call Logs backup & restore | APN Settings Backup & Restore.
• The Phone Contacts can be synced with your Gmail account. If you don’t know how to do that, use this guide here.
• Enable USB debugging option.
• Charge the I9300 battery so that the device won’t power OFF during the ROM installation process.
• Your Galaxy S3 should be running on a CM9 Nightly build ROM. Here’s a guide that teaches you how to update it to CyanogenMod9 Nightly ROM.
• Install this ROM only if you’re interested in testing Jelly Bean and the CM10 Alpha build. If you cannot complete the installation then you should use the comments section to ask for help.

Now that you’read all of the above, you should move to the tutorial guide and install the preliminary build of CM10 on your Galaxy S3. Make sure that you apply all the steps I’ve listed and in case you can’t finish the Cm10 Jelly Bean install then you should post in comments.

Install CM10 Jelly Bean 4.1.1 Alpha ROM on Galaxy S3 I9300

1. Download the CM10-based ROM from HERE. Save the file on your PC. Do not unzip the file.
2. Download the GApps zip for Jelly Bean ROMs file HERE. This one will install the Google apps on your smartphone.
3. Next, connect your device to your PC and move all these files on your phone’s internal sdcard. After the transfer is complete you need to power OFF the device and then boot into CWM Recovery.
4. CWM Recovery mode can be launched by pressing and holding ‘volume up’ + ‘home’ + ‘power’ buttons simultaneously. When the I9300 screen powers ON you should release these buttons as the CWM Recovery will now load.
5. When in CloworkMod Recovery main menu you should first select ‘wipe data/ factory reset’. Confirm the process and move to the next step.
6. Next, select ‘install zip from sdcard’ and from the next menu you should select ‘choose zip from sdcard’. Find the ROM zip file of CM10 and then confirm that you wish to install.
7. When the ROM has been installed you will have to repeat step 6 and flash the Gapps zip file. When the Google apps were successfully flashed you should return to the main recovery menu.
8. Select ‘reboot system now’ and confirm that you wish to restart.
9. Now, your device will perform the first CM10 alpha ROM boot and you should give it at least 10 minutes to complete it. In case the first boot takes way too long to complete, then you should remove the phone’s battery, re-insert it back on and then repeat the entire tutorial once again. If the ROM has booted normally then you’re done with this post and you should start testing all its features and Jelly Bean new services.

These were all the steps you had to take. In case you have any other questions, leave them as comments at the end of this article.