I've bought Samsung Galaxy S Duos 2 gt-s7582, it shows android version 4.0.4. The main problem is with the RAM, it shows only

[vinosee]

I've bought Samsung Galaxy S Duos 2 gt-s7582, it shows android version 4.0.4. The main problem is with the RAM, it shows only 214MB total RAM while actual RAM is 768MB. Is there any way to unlock remaining RAM as 214MB ram is very low and phone lags very much in menus and programs.

 

[Titillating]

That RAM is likely being used up by the OS itself and whatever apps you happen to be running. TouchWiz is notorious for using lots of memory. You can go into your system menu, find the tab for applications, and try to disable as many of the unused Samsung apps and services as you can. There's not much else you can do about it unless you want to root your phone and use a custom ROM or a de-bloated one.