ie 4.5 with juce library on windows, offcourse it means that my GPU and graphics driver should support that version of API (it does).
That is far from sound logic: because your driver supports something recent will definitely not mean everybody else's does! The range of cards and drivers still in use is massive on Windows - so you have to wisely pick your API based on your target market!
Sorry for a naive questions, but i was wondering if its possible to take advantage of the latest OpenGL api
If JUCE doesn't have the functions you need already loaded for you, you can load them manually.
For whatever JUCE loads, see OpenGLExtensionFunctions (https://www.juce.com/doc/classOpenGLContext#a3e204724fd78bbc272023525226caad7)
The OpenGLHelpers::getExtensionFunction method will load OpenGL functions for you, or return nullptr if they're not available.
You should be able to add JUCE_OPENGL3=1 as macro to your Windows project in order to work with whatever functions JUCE's loads that are OpenGL 3.