[AC Question]

My device is Galaxy J2. Android Version 5.1.1. Model Number SM-J200GU.
Whenever I check for Software Updates, it always says the latest updates has already been installed.

Nougat is coming, and I still haven't received Marshmallow. Other people I know, they have Marshmallow already.

[Tim1954]

Have a look in Sammobile. Type in your device model number (SM-G930F for my S7 for example) and you will see the current available sofware.

[chanchan05]

Because it's a J2. Meaning its on the budget model list of Samsung. These phones typically aren't updated because Samsung isn't spending money on that model to keep it 'cheap'. The higher end models are the only ones getting update treatment.