Q1: yes on physical fit. Will need smallport ecu to match
Q2: a) Take cap off and look for toothed wheels, bigport has a 24 tooth wheel and a 4 tooth wheel. Smallport has a 24tooth wheel and a wonky round thing with a blip in it.
Q2: b) yes, interchangeable
Q3) top dead centre, look through oil filler hole find the indent on inlet cam. If indent isn't there, spin the engine 360 degree and it should be there, otherwise, something's wrong with cam timing/timing belt. Line up the dot on dizzy gear to dizzy body and stab. Look in the manual in the tech articles or something for a more detailed way.