CBSE 10th

Yes, you can take up a Diploma in interior designing after 10th. Alternately you can do 10+2 and then do a Bachelors in interior designing. The latter is a better option in fact in my opinion.

Oh yes, you can choose the sciences - Physics, chemistry, mathematics. Computer Science and electronics are optional subjects given to you in some colleges. Thereafter, you can do engineering in computer Science, information Science or other courses like electronics, telecommunications, instrumentation, electrical etc. And still get into IT field through a relevant job. After 12th, you can do Bachelor of computer applications or Bachelor of Science in computer applications and IT.

Totally depends on your skill sets and interest. Talk to alumni from both the fields and do a lot of online research and then ask yourself the right questions to arrive at a informed decision. Biology (Sciences) leads to Bachelors in medical, nursing, dentistry, physiotherapy, botany, zoology, biotechnology, bioinformatics, genetics, chemistry. Commerce leads you to accounting, finances, economics, statistics. ICWA and CA are relevant qualifications.

You can take up Diploma in interior designing after 10th. However, if you want to do 10+2 in any of the streams like arts, sciences or even commerce and then do a Bachelors in interior designing, it is also a great idea. Some of my friends have done Bachelors in Science, commerce or arts and done a separate Diploma and a certificate course in interior designing which works well too.

Since you have a Diploma, get few years of work experience to get good hands on exposure or even an active internship. Post that, if you think you want to continue with Bachelors for higher career prospects. You will also know what exact specialisation course to highlight and study at Bachelor level.

There is no one important course. Take up a course based on your interests and skill sets. Arts, Commerce, Sciences are 3 broad categories in 11 and 12. Alternately, Diploma and certificate courses can be taken up to. For example -
Arts - Languages, psychology, journalism and media, humanities etc. Sciences - Physics, Chemistry, Biology, Mathematics, Computer Science, electronics
Commerce - Accounts, economics, statistics, ICWA and CA thereafter.

You may consider doing through 3 entry points - Diploma, Bachelor or even certificate courses. Course options are hotel management, culinary arts, food and beverages, catering technology, bakery and confectionery, food production. Complete 10+2 and then do the Bachelors in the above options. Its better.

You are eligible for both engineering and medicals. Depends on your interest and skill sets now. On the other hand, you can do Bachelors in Science in diverse options across physics, chemistry, botany, zoology, genetics, bioinformatics, biotechnology, computer applications and IT etc. Alternately, even Bachelor of computer applications or Bachelor of business administration is available. If you want to change path to hotel, hospitality or travel and tourism, its possible too,. .

I recommend you to take up 10+2 in Physics, Chemistry, Mathematics and optional subject Computer Science. Do the entrance exam preparation during 11th and 12th for getting into engineering. In the graduation stage, choose computer Science or information Science engineering.

You have diverse Diploma options. Example, Diploma in arts, animation, beauty culture and hair dressing, cosmetology, hotel, hospitality and travel and tourism management, various option of engineering, fashion designing, interior designing or other designing like textiles, apparel, jewelry.