[G2 Q&A, Help & Troubleshooting] raulx222:
Welcome!

Firstly you need to read all things with attention and do things carefully. And keep in mind, don't blame me if something goes wrong and you brick your phone. I dont want to scare you with this, but i also don't want to be blamed if you don't pay enough attention.

If your phone is already rooted and running a custom ROM then you need to know some things. Right know you have installed on your phone a custom recovery menu. With that custom recovery menu you are able to flash(install) new ROMs, kernels, and different files on your phone but you can also backup/restore your data from/to your phone(including the EFS partition)!

Some tips! I will show you how to upgrade to CloudyG3 but also you can check the methods on youtube, like "How to flash new ROM with TWRP" or "how to backup/restore from TWRP" just to be sure that you dont do something wrong. And when I give you a link, you should read from that pages too and dont go directly to the download section!

Before starting, look into settings -> hardware information and find out which model of G2 you have (d800/d801/d802/f320/..etc) and keep your model number in mind and dont forget it :D and always download things only for your phone model! If you download the wrong version, you will brick your phone

Now, if you want to update to CloudyG3 2.1 then I recommend you firstly to update your custom recovery menu. From here you can download the latest version of TWRP (this is recovery menu) with some new features baked by blastagator :D.. be sure that you download the version for your phone model!

How you install the new recovery menu? Just copy the .zip file on your phone, then hold power button and press "reboot recovery menu". Your phone will boot in your current recovery menu, then go to "install" and select the .zip file that you just downloaded and flash it! Then reboot to system.

Now you can update the ROM! But firstly backup your data. Go again in recovery menu then to "backup" and check all boxes and do backup. Always is a great idea to keep a backup on your PC, at least for EFS partition. EFS partition contains things like IMEI, this is maybe the most important thing that is stored in EFS so always keep a backup of EFS!

Now, download CloudyG3 and put the zip file in your phone. Then reboot in recovery menu. Now, I strongly recommend to wipe your phone data and do a clean installation of CloudyG3! If you dont do a clean install then maybe you will face different problems, but its your choice. Doing wipe you will lose all apps and settings but your files from your phone storage will remain intact. How to wipe? In recovery menu tap on "Wipe" and do a factory wipe(system, data, cache) just "Swipe to wipe" ( do not touch other things!)

Then tap "back" and go to install, and choose the CloudyG3 2.1 zip. It will open a AROMA installer, follow the instructions on the screen. Again, be sure that you select your phone model when you install CloudyG3..after installation, boot into system and done! That should be all.

Feel free to PM me if you have questions, rather ask somebody than do something wrong :D

And please excuse my english, ask me if you didn't understand something.