1 - Depends on where you are. If you're in a rural area, often you just skate on frozen lakes and ponds. There aren't nearly as many outdoor rinks as there used to be, due to legal liability if someone slips and cracks their skull. Just another negative effect of our increasingly litigious, PC society.

When I was a kid, every park and schoolyard had outdoor rinks.
2 - The majority of high schools have a boy's hockey team and many have girl's teams, (Provided the student body is large enough). Ice time is expensive so most high school teams rarely practice.
3 - There are thousands of minor hockey league teams in Canada. Research the GTHL if you want an idea of minor hockey in Canada. Your best bet is the local House League. At 17, I believe you would be in the Midget age group. House Leagues are open to anyone that wants to play, regardless of skill level and the costs are affordable. The most competetive levels of minor hockey in Canada can cost upwards of $10,000 per year.