The Explode button is available if you go to Forzavista via the Career menu but not if you View Car when selecting from My Cars. (at least, I have the Explode button in Forzavista right now).
I can’t open the hood on the Escort Cosworth either, but not all cars can, and I think it’s been that way since before the recent updates. Also, I haven’t tested this but I’ve heard that if you upgrade the aspiration on your engine, the hood will become locked.