Accounting & Commerce

Yes for preparation of civil services, it would be beneficial. But you continue with commerce that would be more beneficial for you.
Good luck.

Since you have completed your class 12th with 86% marks, so getting SRCC is not possible, but you can definitely apply in DU for UG course. There, all you need is to fill up an admissions form, then you will be shortlisted according to the college cut off list.

B.Com is graduation for commerce stream students, you will study accounts, costing, financial management, statistics etc. After this, you can apply for further for post-graduation or any competitive exams like banking, SSC etc.

Instead of certification, please do an internship in the related area where you want to make your career and participate in the organizing committee of your college festivals in the coordination, event management, budgeting, etc as it will add more value.

You may pursue any classroom-based or online certification course related to a particular stream of Marketing like Digital, Email, Social Media, AdWords, Search Engine Optimization, etc based upon your liking. Digital and Social Media Marketing are some of the current trending things in the field of Marketing. I have no idea about the classroom-based courses, but you can visit platforms like Udemy, edX, Coursera, etc. for pursuing any online course(s) related to your area of interest. I hope it helps!