How can I check what is left on my pass?

That is very simple the hop on off buses route starts with 3 or 5 route once u cover one route ...u will finished the sight seeing spots of that route... Otherwise cross it or mark it on the route map of the hop off hopp on bus paper👍

Damn, good question, the pass entitles you to access each attraction once during its duration except for the hop-on-hop-off buses that you can use everyday of your pass. So simply if you have visited the attraction then its essentially crossed of your list, the list of attractions is available within the app.