Colleges in Patna

It is one of the good colleges in Navi Mumbai for electrical. There are several other best colleges like SP college, VJTI, Amity, etc.

Yes, it is good option for BioTech.As you know MGM is best college for Medical also.They have upto-date equipment also in biotech branch.

It will be based on based on your branch. If it's Mechanical engineering it's somewhat tough, and if it's Computer Science it will be easy.

Yes, you can surely apply and with your performance in GDPI, you can even get good results too.

There is this Mahatma Gandhi Central University - MGCUB, Bihar where most of the students get placed in decent companies and also, the faculty members are very helpful there. In Maharashtra, you can try Narsee Monjee which is one of the top colleges in Mumbai with very good placements. Also, check this link for having a look at the placement reviews at St. Xavier's College, Mahapalika Marg, Mumbai- https://www.shiksha.com/accounting-commerce/course/b-com-st-xavier-s-college-mahapalika-marg-Mumbai-110121
As compared to Bihar, Patna, there are so many good colleges in Maharashtra, with good placements.

It differ from university to university.
Some university also take admission of commerce students, but if you don't have Maths background in class 12th, it might be little difficult, but if you can catch up that, I think a commerce student can also apply for BCA course.