Career

Hello Vishwesh, there are institutes in Delhi that provides free coaching for upsc to SC/ST students.

Last date of admissions in Architecture colleges across India would be around 1st of August, but I would suggest you not to wait till the end. you will get the institutions approved by Council of Architecture, the competent authority for Architecture education here on this link
https://www.coa.gov.in/index1.php?lang=1&level=0&linkid=25&lid=26

Both are equally good and it depends on a lot of other factors which you need to look into from a personal perspective.

Yes definitely you can pursue architecture. Architects have a lot of opportunities in various fields, such as
Entrepreneurs
Architects (Junior/ Senior)
Furniture design
Photography
Construction& Community based volunteering
Infrastructure development
Graphic design
Set Design
Jewelry design
Advance research in Architecture
Faculty @ School of Architecture
History, Restoration and Preservation
Interior design
Product design
Landscape Design
Project/ Construction Management

An Architect has got a lot of opportunities, such as
Entrepreneurs
Architects (Junior/ Senior)
Furniture design
Photography
Construction& Community based volunteering
Infrastructure development
Graphic design
Set Design
Jewelry design
Advance research in Architecture
Faculty @ School of Architecture
History, Restoration and Preservation
Interior design
Product design
Landscape Design
Project/ Construction Management

Complete your left over papers first. Try for a job and gain experience. Do some short term/online courses related to your engineering while working. I mean "EARN AND LEARN" simple. All the best.

For cracking civil services examination, the type of graduation does not matter. For success you will have to develop deep understanding in subjects of your choice. In order to excel in exam you must choose degree based on your interests and personal strengths.