what stream i should choose in 11 for designing?

there is no particular stream for designing, but if choose commerce thn it will beneficial for you, for more query plz mail at rathorek24@gmail.com

For degree in fashion design passing 12 is compulsory.

Prefer science-Maths stream as it would give you a scientific bent of mind and would keep other avenues also open. PCM group of subjects is also more near to designing aspects. You may choose Computers as your special subject to learn designing on computer also later.