1) the xoops question has been asked today already. the topic is in the same forum. short answer: yes, theoretically it can, but noone has written a xoops integration yet. so there's much work to do.
2) with a litlte work, yes. work = the popup, not complicated.
if a click should just open a new windows with the image in gallery, then the answer is yes, and no work is required.
g2's imageblock module can be used for that.