Degree

Yes, you can get admission in Karnataka or another state through lateral entry.

Yes, you can do your degree after your Diploma, but you need to pass 10 +2 to enter graduation study which you can't do on diploma certificate at least not in Karnataka.

Goa Institute of Management, IIHMR, Tapmi, Symbiosis.

Your profile is very good. You will require following things to apply an American university for undergraduate degree:
1) SAT, SAT subject test and TOEFL score
2) Two teacher's recommendation
3) One counselor recommendation
4) Your 9-12 grade marks
5) Your personal essay
6) Extracurricular activities which you have already mentioned. Feel free to ask questions.

I think it is easier in comparison to other universities because they don't really have a limited capacity and can admit students purely based on merit. There should be some requirements posted on the website, and if you fulfill the requirements then you'll be admitted. For more details, you can get in touch with the placements companies as they would have all details about the same.

Hi, you can, but it depends on the college or university. You must speak with them first and check for availability and requirements.

For admission in MA psychology, you must have a graduation degree in relevant stream from any recognized university.

Hi,
PG is done with graduation percentage. So, you cannot apply or get admission in any PG without graduation.

Yes, degree of any technical course is valid.