Hi, Doing diploma in Interior Designing and Decoration is a wise decision only if you do it from a good college and the Diploma Certificate is approved by Government of India.
After your 10th you can join an Interior Designer firm or consultancy where they would accept at the very entry level position. There you can gain skills and then setup your own interior designing business. There are various types of jobs opportunity such as spatial designer, lightning designer with the average package of INR 2,00,000 per year
You can either go for diploma in interior designing or a bachelor's degree in interior designing after your 12th. But make sure you join some reputed college so you get networking chances and placement activities. The package is almost same as first but it has its benifits such as practise and the salary increase as your experience.
Bachelor of Architecture in Interior Design is a 5-year full-time undergraduate course, the minimum eligibility for admission to which is the successful completion of the 10+2 level of education from a recognized educational Board. Graduates can expect to get an entry-level package of Rs. 10,000 to Rs. 15,000 per month. With experience, you can expect your salary to reach up to Rs. 30,000 to Rs. 75,000 per month.
You can choose according to your preference but practice is what most important in interior design.
Hope this is helpful
Thanku