I want to compare values from two different files.
In Notepad++ version 5.0.3 we had shortcut button Alt+d but in version 6.6.8 I cannot find any option to compare.
Also let me know which version is most stable.
There is the "Compare" plugin. You can install it via Plugins > Plugin Manager.
Alternatively you can install a specialized file compare software like WinMerge.