Can I use QtGui instead of glew/glfw/SDL library in Qt for OpenGL?
Read this(from the Qt website):
It says that it provides OpenGLin it.
So can i use QtGui class instead of glew/glfw/SDL library for OpenGLwork?
Yes you can. If you're already using Qt, you have the advantage of everything else also being Qt, otherwise you might (depending on the other framework) need to handle e.g. input in a special way.
You could use Qt to get a platform window and an OpenGL context for rendering. However, Qt is a huge framework, and it doesn't make much sense to go for it if that's all you need.