Give search for home theatre door in houzz and it will give you a few ideas. But finally what you have to think or take help from interior designer is about the theme of your home as this door should also get aligned with your house theme. In general having hallway as part of home theatre is not advised so if you can change it, it would be better. But if you can't then at least install auto closure.

I might sound weird ( word meaning says "suggesting something supernatural") Take some markers , sketch 100 pages on your printer pages, look where you stand on this test, you might go wrong on first 10 sketches but later you'll bloom.once this is done. Take neufers or interior design standards , check your technical skills with furniture sizes. and don't forget you already have a technical education. and first and the last things "never underestimate yourself". I know a carpenter who owns 15 hardware & ply shops who cant speak English. Further Make a portfolio of the work done above, learn some auto cad/ revit. To be very true, if you are good enough you might lead a bunch of draftsman's / architects straight away.

Dear Narayana, Interior Design fee vary from designer to designer and also upon the scope of work. Some may charge per square feet basis while some prefer as lump sum as per the total cost of the project. It also depends on your personal taste and understanding of the interior designing. The fee may vary from Rs. 50-500/sqft. Kindly go thru my profile and check out my interior projects and let me know if you want professional help. Thanks

SInce it is a compact apartment as most apartments are, having minimal decor with maximum storage will do best justice to the flat. U can have a storage cum visual space seperator which keeps the drawing room seperate from the private areas. The bedrooms can also be kept simple with storage beds, having sliding wardrobes with mirrors which gives a feeling of space. the kitchen also can be kept simple sleek with few highlights.