Don't spend the money to match the exterior finish of the cabinetry on the cabinet interiors, you want the interiors to be easy to clean and a light material so you can see what is inside them. No one will notice or care if the interiors match the exterior (these days it is pretty much industry standard that they do not match) If the cabinet doors have glass fronts then definitely match the exterior or use a pop of paint color on the cabinet backs.

u should go for the olive green sofa.. it's clean neat design.

Ok so go for ambient and cool colour wallpaper behind the wall. You can have same colour in ceiling that of wardrobe and make other wall plain light colour.

I've seen a lot of photos and I have come to realise that I really like the pastel/muted color pallete and have also come to know that they are good for small rooms. I really liked nickel grey and silver grey. Do both of these colors also belong to pastel color pallete? I am not able to find a separate section for pastel color pallete on asian paints' website. So it's difficult to find similar colors. Thanks for helping me.