Samsung will not release Android 5.1.1 Lollipop update for Galaxy S3 Mini, but tech savvy S3 Mini users can enjoy Android 5.1.1 Lollipop on their device by installing CyanogenMod 12.1 custom ROM. Lollipop brings new interface and features to the phone. Also, as CM12.1 is an AOSP based ROM it will give near stock interface to Galaxy S3 Mini.
The below guide lets you know the Android 5.1.1 installation procedure for Galaxy S3 Mini. This is an unofficial version of CyanogenMod 12.1 ROM developed by Novafusion that supports all variants of Galaxy S3 Mini such as i8190, i8190L and i8190N.
The ROM status is stable, but there are few minor issues. Video taken by camera is green that you can fix by installing an open camera app. In addition, few users are reporting issues with mobile data, which can be fixed by adding new APN manually with proper settings for your carrier. Interested users may read on to know how to install this ROM on Galaxy S3 mini.
Requirements: Galaxy S3 Mini must be rooted and newest version of custom TWRP recovery [Download HERE] installed.
Important: Back up everything on your phone – contacts, call logs, SMS, images, video, audio and EFS data. Also, DO NOT forget to make Nandroid back up from recovery.
Warning: Please follow this guide at your own risk. Though we are putting our level best to provide this tutorial at its maximum perfection and accuracy, we can’t take responsibility for anything that goes wrong. This guide is intended for technically talented users only.
2. Now, turn off Galaxy S3 Mini and reboot it into recovery mode. To do so, press and hold Volume Up, Home, and Power button few seconds.
3. From recovery, wipe cache partition, dalvik cache and wipe data/factory reset
4. Now, select Install, choose cm12.1 ROM zip file and then use slider on the bottom to let process begin. Do the same for Gapps zip file also.
5. When installation will finish, use Reboot to system option to boot your phone.
Enjoy Android 5.1.1 Lollipop on Galaxy S3 mini (source)