steelhead and salmon life history?

I have several questions.
1) At what age do chinook and steelhead leave for the ocean? (I have
caught chromers from 11 - 17 inches that both seemed like juveniles, I
take it steealies dont go to the ocean till after they are at the age
that they are 17 inches?)
2) I have caught juvenille steelhead but never juvenille chinooks. Do
chinooks immediately go back to the ocean?
3) do steelhead come back to the river before they are adults just to
hang out?
4) This is really dumb, but have any studies been done to see what
happens if salmon are transplanted to the ocean after they spawn? Yeah,
they would probably die like they do in the ocean. But maybe they just
dont want to make the trip back and if they were transported they would
continue on