MHT CET is Maharashtra Common Entrance Test. MHTCET is state based entrance test which provide an opportunity for students to study in maharashtra based colleges. 

If you want to complete your studies in maharashtra based college then MHT CET is important else you can give other entrance test.

Same is the case for B. Arch. If you want to pursue Architecture in Maharashtra then you can apply for MHT CET else it is not compulsory.