You are allowed to replace a player if a player on your team gets injured or gets cut. Once the pucks drops for the tournament all rosters cannot be changed.
I guess all tournament games will count for points(even relegation games).
Here is the breakdown of players picked from each country
Canada-19
Sweden-11
USA-11
Russia-10
Finland-9
Czech-4
Slovakia-2
Germany-2
Switzerland-1
Norway-1
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