Certificate

Yes, you can get admission if you have cleared 12th in any discipline from a recognized board.

For pursuing Certificate Programme in Food and Nutrition there is no formal academic requirement and the minimum age is 18 Years in Dr. B. R. Ambedkar Open University.

Yes, in many government jobs, if candidate has done O level certification, then B.Tech ECE candidate is also preferred. Normally, B.Tech in CSE or IT is preferred, but with certificates, the candidate is eligible for applying. Also, it depends on company to company. Before applying you Can check the eligibility criteria.

EdX is an open online course providing website that provides the reputed courses from various Universities and colleges by charging a minimal amount of money. Some of the courses are even free of cost. They certify you the course after its completion as well.
Yes, it boosts the chances of getting admission in USA's top universities.

Certification is a good choice. MBA could be a better option if you feel the subjects are of your interest. The job opportunities after MBA with a good salary package is definitely high. You can also choose a different stream after completion of a year, according to your interest and choice. It is a stream where you can develop your personality and groom yourself along with the completion of the course. SPPU would be the best to do MBA.