Loading a Movie into the scene at a certain frame?

Hi im trying to build an image veiwer for my website,
i have four pics that if you click i want them to load the image veiwer and start at the image you’ve selected (i.e. start a certain frame) then at will you can scroll through the rest.

i’ve got as far as loading the image on demand

im stuck on:
how to start the movie at a certain frame?
and how to exit and return to the original movie?

Similar to this only instead of lots of mini image viewers i want all of mine on one timeline:

Thank you :wink: