Is it possible to pursue PG in Architecture after completing civil engineering?

In my opinion you cannot go for MTech in architecture if you have taken civil engineering for BTech. Check this from some good sites like PSG, LPU, BMS etc

Yes, surely you can do that and many people who find their interest in architecture do the same. If architecture is more interesting for you then you should opt for that after your B.Tech. Hope this help :) .