Wikipedia (at the link below) lists 90 active Catholic Churches in Venice, and an additional twelve on the Islands which are part of Venice.
Many Orthodox churches have a dome because it represents Heaven. Many Catholic churches also have domes, such as in St Peter's in the Vatican and St Mark's in Venice.
Zero
I believe that there are 30 Catholic parishes (churches) in Rome, Italy. I did a search on Masstimes.org and it listed 30 in Rome.
No. Many Protestant and Orthodox churches also name their parishes for saints.
Most of the people in Venice are Catholic.
All churches have catechisms. In the catholic, there is called a Cathechisms in the Catholic church.
I think that there is just 1 in Quebec surprisingly. I am doing a research project on the churches in Quebec and I havge only found 1 Catolic church. Sory if this is not helpful. :P Although there are not as many churches in Québec City as in Rome, the city of the "300 steeples" or Montréal the city of the "100 clochers", there are a great many Catholic churches in Québec's capital city.
In Catholic churches.
The link below lists all the Catholic Churches in London.
Roman Catholic Diocese of Venice in Florida was created on 1984-06-16.
The Catholic Directory lists 42 Catholic Churches in Miami, the list is attached at the link below:
The majority of churches and monasteries in Romania are orthodox. But there are many Catholic or Protestant churches. Do not miss even a few synagogues and mosques.