Game engines, the choise of language

1,For editor gui, Cryengine3 use a charged library that like mfc(c++) and developed by other company.but I have forgotten its name.
2,Unreal and Cryengine are both separate engine and editor in different project, engine is kernel project.
3,In my opinion, I suggest that you should use c++ because of it portability.
4,Sorry about this question, but I think that using VS should be ok, and they may be develop it in Multi-Platform OS(win, linux,etc...), to make engine cross-platform available.

microsoft themselves are not using visual studio. but they use their compiler and nmake. Epic must be using it at least for some part since the SDK has a plugin for it.
as for GUI, it does not marry well with 3D engine or even 2D. Most big companies redo all the UI in a custom way to integrate it in the accelerated surface. (i.e, like Blender). In any case, MFC is deprecated and should not be used directly. Win32 SDK is barely better, it should only be used by middleware vendors, like Nokia for QT but any Coder joe should never have to include windows.h.

An engine is mostly separate library (although it can be used as framework and built into every code) - it depends, do you want your engine to be a module for your game (e.g. when there is bug in it, you just fix the library), or do you want it to be part of the game project (e.g. it's a big monolith). Both has it's advantages and disadvantages and it really depends. The question is, do you want to use same version of engine in more of your projects (then DLL probably wins, although both ways can be used), or whether you want to use single engine version in single game (where either is good, maybe framework a bit better - because you manage just single project).

As for the language used for the game engine - it can be any, I mean like you can use any procedural (C, Pascal), object-oriented (C++, Object-Pascal, or higher level C#, Java), or even functional (Haskell) - e.g. you can actually use ANY usable language out there.

First of all it depends which language you know (and I mean you know well). You can go purely procedural with C - it has it's advantages, no inheritance, polymorphism, template (etc.) mess - so in the end project looks a lot simplier, on the other hand absence of these will make your code a lot longer. You can go purely OOP - but it has also it's problems, you can mix these two (this can end in either very good code, or in bloody mess) ... it's all up to you. I've been working on engine in both major - purely procedural manner and object-oriented manner - yet I can't tell which is better, both is good and both can be used well. I've never tried to write purely functional engine (in Haskell), but one day I'd like to try (but it's definitely possible).