Is it possible to get admission for architecture(B-Arch), after having completed 1st year of Pre-University(XI), without the completion of 2nd year of Pre-University(XII) ? If yes? Which are the places available and where can I get it done ?

You have not stated where abouts you live and intend to study? I presume this is in the US? Unfortunately I do not know the system there (I am a UK based architecture student) so the advice I can give is limited.

The most important thing you need to work on when applying to architecture school (in the UK) is the portfolio. A good portfolio will outweigh grades and academic achievements. In order to prepare a portfolio, explore areas outside of architecture. Ie: Architectural education is not about legislation and standards. It is about exploring unknown territory, challenging yourself as a designer, and finding an area which interests you, and will influence your career for the next 50+ years! Read up on different areas of art and design. Look into product design, graphics, motion (film), photography etc... Read, write and draw simultaneously. They will be useful when you begin studying architecture. More useful than many subjects which are considered 'academic'. Also, start to think about how you will answer the one question which every school will ask, 'Why do you want to study architecture?' You best have a good answer if you want to get into the top schools!!

In summary, I don't think there are necessarily strict requirements in terms of grades or subjects at most schools. They should (and often do) recognise that the ability of an individual as a designer is not directly dependent on their academic ability, or previous achievements. If you can demonstrate a passion and interest for the subject then that is what they are looking for. However, architecture is a demanding, and rigorous seven years of study. You will also need to demonstrate that you have sufficient motivation and focus to complete the course. Therefore, it may be worth considering completing your second year, and then joining architecture school.

Which schools are you applying to?