Science

Sorry, but you cannot do BCA if your optional subject is not mathematics.

Amity University Rajasthan do not offer this course.

No, there is a proper selection procedure for admission:
The online test and interview will be conducted in the first half of May 2019 at Mumbai, Chennai, Delhi, Dehradun, Chandigarh, Bangalore, Kolkata, Hyderabad, Lucknow, Indore, Ranchi and Jaipur. Candidates will be shortlisted based on marks in PCM, online test, IMU test rank and interview. The selection is also subject to medical fitness a per DGS norms.

Candidate must have passed 10+2 from a recognized board to get eligible for the course.
https://www.shiksha.com/it-software/course/m-sc-computer-science-modern-college-of-arts-science-and-commerce-progressive-education-society-shivaji-nagar-pune-204159

You can do B.Sc in a field of your choice.

IN TU - Tantia University, there the part time Ph.D is not available. It is there at LPU. Duration of programme is minimum 3 years. (From the date of initial registration). To have detailed information about the programme, please check this link- https://www.lpu.in/programmes/part-time-phd-in-botany

In case you have lost the application form, then the only way is you buy a new form again and fill that up.

Yes, your score are good to go. Please check the complete eligibility criteria here: https://www.shiksha.com/science/course/b-sc-in-agriculture-tamil-nadu-agricultural-university-coimbatore-313909
Admission is based upon counselling based on the marks, scored in TNAUEE i.e. Tamil Nadu Agricultural University Entrance Exam.