Hello,
Diploma in interior design is a 1 year basic certificate course which mainly focusses on fundamental needs of the industry and tries to maintain a supply and demand mechanism in case of industrial demands and delivering of qualified professionals.
B.Sc is a 3-year programme and B. Des is a 4-year programme. B. Des in Interior Design will carry more professional study from a good foundation learning to professional assignments, work projects, modules and a curriculum that is more industry-specific.
B Des interior design is a more practical and professional approach.
You can go for Master in interior design once you complete your Bachelor's degree.
Masters in Interior Design is a more advanced level dgree of Interior designing.


Hope it helps