They do expect that you have some specialization (see "...depending on your specialization...") and they seem to offer multiple internships. That's the tough question you have to answer now - market yourself as generalist - or do you look stronger just presenting a certain side of yourself. What do you want to do most?…
yup, better keep it short. For a lead position it can be long, because you'd like to talk about some stuff that cannot be put in the resume to catch some attention. If you want to shorten it, just remove all the stuff they can find in your resume and folio anyway (e.g. where you worked before, what other skills you have).…