Maya, what is your question? And please post pictures or a sketch of your floor plan for us! Or both! We're very visual people and the pictures help!

My drawing room front Window is going to be of around four feet wide. As the width of this room front wall is 10 feet out of which 3'6" will be kept for front entrance door. I am confused whether the sill height of the window should be 6 inches or 3 feet high as sofa is coming in front of it as my drawing room size is 10'0" * 14'0".

First of all the images you posted you cant make anything out what you got there. Secondly you should contact a local Architect when doing something like this, not only for structural reasons, but window design as well. He will layout window detail based on the window sizes available from a certain manufacturer or you can take his drawings which indicate opening detail to a place who sells windows, and they have catalogs of window combinations and sizes to make it work with what you have.

the design looks great . According to me one side of windows can be used as bed wall . we can have blackout curtains or blackout window blinds . You can even play with drapery to define the area behind bed. We already have seating in the room so next we can do is give a console/ study table with an puffe / chair to it. also one can add a bench at the end of bed. Size you can check on your Autocad . Bed wall should be the focus when one enters the room, so I feel the bed should be placed like this . Dimensions of furniture and circulation space you can work on. Also WC should be on the washbasin side to avoid Future leakages and dampness in bedroom wall. all the best