How can I upgrade Android OS on my AT&T Samsung Galaxy S II from 2.3.4 to 4.0?
Since your phone is an AT&T sgh-i777 I guess you are well past your warranty period. Moreover if you are using it in India you never had one :-PI too have an AT&T galaxy s2 running a custom Rom. So my suggestion is root ur phone after going through the steps mentioned in the below link of xda developers forum and install a custom jellybean 4.1.2 Rom.http://forum.xda-developers.com/...Please be careful about bricking the phone if you don't follow the steps properly.
How do I update my Samsung Galaxy Duos S7582 from 4.2.2 to 4.4.5?
Your phone doesn't have software support anymore, and android 4.2.2 is the latest official firmware it will run on.You can find custom ROMs on XDA developers, and tutorials of how to flash them. There's no official way to do this.Samsung Galaxy S Duos 2 Forum on XDA Developers
Will the Samsung Galaxy Grand and Galaxy Note get updated to Android 4.4 (KitKat)?
I don't think there is a possibility that Samsung itself will upgrade them. As they have a policy of leaving 2 year older devices with no further updates.Still there is a way to upgrade them by rooting. Rooting is a risky process and needs some geeky knowledge. I have become a power android user by rooting every phone I ever had.U can Google yourself if u eant to take risk.
My International Galaxy Note 2 (on Android 4.3) says my device is modified when I check for software updates. What can I do?
This is because your Flash Counter has increased. First of all, you need to root your device again. You need to use Triangle Away app available in the play store/xda developers forum. Then, reset the flash counter back to zero.After that, you need to download the firmware with the same build number as your current firmware(important if you don't want to lose data! Make sure you have a backup of all files present in internal SD), which can be seen in the 'about device' section in settings. Download from here: Everything for your Samsung Mobile. Then, download Odin and read tutorials on how to flash firmwares to your Note 2 using Odin. I'm not 100% sure about this method(new Knox counter has been introduced in 4.3 too), but I think it will work!
How can I update my Android version of Jelly Bean 4.3 to KitKat 4.4 in my Samsung Galaxy S3 phone?
Samsung is very slow in providing updates so if you are very keen for update root your smartphone.After rooting you can also use net-cut for android for increasing your WiFi speed and there are tons of other customization’s available after rooting.But rooting will render the warranty of your phone null and void so read properly all the instructions before rooting your phone.