B.Arch

No you cannot apply for B.Arch course without studying 12th with Science stream. I will suggest you to do BBA then MBA course. BBA course will give you an exposure in management field. After completing BBA you can go for MBA. MBA will provide highly challenging job for you. Different specializations are there in MBA. If you are looking for a career in marketing, then MBA in Marketing is a good option, Because now a days mostly companies recruited students for marketing jobs. The Bachelor of Business Administration degree is considered by many as the degree of the future. It is a professional degree that is rising in popularity among students who want to make a career in management right after their 12th standard exams. This degree is also apt for students who want to pursue management studies after graduation. With a BBA degree, they already have a strong base in management studies and they fare better than students who are not from a management background. Best Universities
ITER Bhubaneswar, Bhubaneswar. Geeta University, Panipat
MSRIT Bangalore - Ramaiah Institute of Technology. SRM
VIT
BITS Pilani
Amity University.

North India:
School of Planning & Architecture, Delhi. Chandigarh College of Architecture. TVB School of Habitat Studies, Delhi. East India and Central India:
NIT Raipur. Jadavpur University. IPSA, Indore. School of Planning & Architecture, Bhopal. West India:
CEPT, Ahmedabad. Navrachana University, Vadodara. Aayojan School of architecture, Jaipur. MNIT, Jaipur. SCET, Surat. Rachna Sansad's Academy of Architecture, Mumbai. Kamla Raheja Vidyanidhi Institute for Architecture and Environmental Studies, Mumbai. Rizvi College of Architecture, Mumbai. L. S. Raheja School of Architecture, Mumbai. Brick School of Architecture, Pune. BKPS College of Architecture, Pune. PVP College of Architecture, Pune. South India:
School of Planning & Architecture, Vijayawada. CSI Institute of Technology, Secunderabad. JNAFAU School of Planning architecture, Hyderabad. R. V. College of Architecture, Bangalore. B. MS College of Architecture, Basavangudi, Bangalore. University School of Design, Mysore. B. V. B College of Engineering & Technology, Hubli. School of Architecture & Planning, Chennai. National Institute of Technology, Trichy. MEASI Academy of Architecture, Chennai.

D.Y.Patil School of Architecture
CHECK THIS LINK-http://dypatil.edu/architecture/index.php
CHANDIGARH UNIVERSITY
Best Architecture College in Punjab, India
Architecture is the art and science of building design that develop the concepts for structures and turn those concepts into reality. Architecture often includes imagination; the ability to order ideas and communicate them clearly; a keen interest in human behaviour, our habitat and the natural environment; and problem-solving skills. In developing designs, architects follow building codes, zoning laws, fire regulations, and other ordinances, such as those that fulfil the universal design criteria. Computer-aided design and drafting (CADD) and building information modelling (BIM) technology has replaced traditional paper and pencil as the most common method for creating design and construction drawings. Architects are licensed professionals and authorized to work with prescribed instructions of the regulatory council.

I can suggest you some other best institute instead of Ganga Institute of Architecture , as I am not much aware of Ganga Institute of Architecture and Town planning. Chandigarh University is North India's fastest growing university.
Eligibility of Architecture at Chandigarh University:
10+2 with 50% marks in Physics, Chemistry & Mathematics & also 50% marks in aggregate of the 10+2 level examination OR 10+3 Diploma Examination with Mathematics as a compulsory subjects with 50% aggregate marks. The candidate needs to qualify the mandatory Aptitude test in Architecture conducted by the Council.
Some recent firm partners with Chandigarh University includes:
UTAA COMPANY (Utah Architects & Architects Co., Ltd.), Seoul
IngenieurbrofrBautechnik GmbH, Hamburg, Germany
AGRAWAL & AGRAWAL, Kolkata
Hiren A. Gandhi & Associates, Ahmedabad
Design and Development, Guwahati
Arcop, Ahmedabad
Himachal Pradesh Public Works Department
K&M Archplans, Nairobi, Kenya
Public Works Department, Manipur
The busride studio, 10-A, Bandra (West), Mumbai
Architect Hafeez Contractor