You can definitely take different section for the theory and lab but it's not recommended. In case of taking a different section, you have to inform your faculty about this issue.

You can only drop courses in your first advising phase and you can't drop any course in re-advising phase. But you can drop them after payment and in the next semester, you will get the refund.

Yes.You can take minimum 2 courses from one trail and maximum 3.

You have to submit all the documents, (application form with necessary department clearance, Intend application, student course analysis, updated unofficial transcript, photograph and other papers ask by Controller office.