shall i join in iit if i get non core like physics,maths chemistry,designing,food&agriculture.please suggest me.

Hi,

It depends on you.
If you are really interested in IIT tag than you must go.
But if you dont care about the tag and want to study any core engineering subjects than choose other options.

IIT offer Msc in Maths and Physics and not B.Tech so technically you wont be an engineer but many students choose these streams for the sake of tag.

Dont worry about placement prospect. If youll perform youll get good placement.
Best of Luck