A ticket is round trip. It's a short boat ride first to Ellis Island and then to Liberty Island. You can spend as much time as you want on each island. Keep in mind the last trip back to Liberty State Park, NJ at the end of the day..Make sure you join the right line back since there is another line for New York.

Noi siamo andati senza prenotazione col battello di linea che ca avanti e indietro Ma era dicembre e non era pienissimo

Service dogs yes, just a regular pet..no

It all depends on how much time you're willing to spend. If your a slow walker and like to take your time i wouldn't go late. If your someone who just looks at the things they find interesting and moves worth a purpose you'll be alright. Photos and reading everything can take time. Also the matter you get in the day things close and staff go home so you might miss things. Yes it will be less crowded but it's a risk.

Pedestal reserve gets you into the pedestal on top of general admission. GA only gets you on the ferries and not into the pedestal.

The crown was closed when I went, not sure.