Hello,
If you go for diploma in Interior Design after your class 10th, your job opportunities will be very less. Also, in the future you won't be able to go for Bachelor's degree or Master's degree as the minimum qualification for them is a 12th degree.

So, you must go for completing your class 11th and 12th first before going for a diploma. Also, after 12th, you can directly go for your Bachelor's in Interior Design which would be a three years course and you would get much vast job opportunities after your Bachelor's. Also, you can go for your Master's degree after that to further increase your job opportunities.

Hope it helps