Connecting transfer at YUL Airport?

Can someone please explain the process of connecting flights in YUL airport? I'm flying from Orlando to an international destination but my first stop is in Montreal. Do I have to pick up my bags? Do I go through customs? I'm going with Air Canada. Both flights.

Do I need a visa to connect in Shenzen, China?

I'm traveling to Thailand in October from Chicago. On the way back to Chicago I'm flying from Bangkok to Chicago with a 4 hour stop to connect in Shenzen, China. All the information online seems to be all over the place on whether I need a visa to connect for my flight in Shenzen. Some say yes, some say no, some say a VOA and some say this particular airport has rules different from other airports in China.

Can I take a 20 stuffed animal on the plane?

I'm domestically flying within California and I was wondering if I can bring one carry on, one personal item, and also my 20" stuffed animal bear that can't fit in a suitcase. I'm flying Alaska Air. Would they let me bring this on the flight?

Added (1). 20inch stuffed animal