Geronimo 33..... My guess reading the wonderful CAA/JAA regulations is yes you would have to do a multi crew IF ride to fly two crew.
No you can't file IF in the 212 single pilot but you can for the 412 as the 212 isn't certified single pilot Instrument. Isn't minimum crew for IFR operation for the 212 two crew???
And the last bit no he can't touch the controls unless you are an instructor rated pilot in the 212.
I'm not saying I'm right with the answers and they aren't the same if you are under FAA regulations (which are so much simpler).