Rome: Borghese Gallery + Colosseum + Vatican
Florence: Uffizi + David
Venice: St. Mark's Basilica + Doge's palace + Bell tower
Milan: Last supper Museum + Milan Cathedral And Rooftop Tickets
Florence: you need specific passes and time-entry reservations to climb the dome (Brunelleschi Pass) or bell tower (Giotto Pass).
https://operaduomofirenze.skiperformance.com/en/store#/en/buy?skugroup_id=3006
The Brunelleschi Pass includes the bell tower as well as the dome, and allows you to climb the tower without a timed-entry reservation.
I don't climb. I made reservation for cathedral tour.
I thought that in another of your many questions (splitting them up confuses me but I'm sure it helps you) we discussed the advantages of the bell tower at San Giorgio looking over at St Marks instead of the exceedingly busy bell tower right in the square of St Marks. Cheaper, easier, more beautiful with better views, and way less crowded. It has a lift too since you don't climb.