There is a stamp collecting club called Vista, they offer free Canadian stamps when you join their site. Once you sign up you can get 25 mint condition Canadian stamps or 100 used Canadian stamps.
No
You can buy stamps online at www.Stamps.com
Canadian stamps are only used in Canada. When mailing a letter, you use the stamps of the country of origin. So only Canadian stamps can be used there.
12 stamps
No, you must use US postage stamps.
No they will not buy back stamps
You can buy stamps at Office Max or Cape Henry Hardware.
Stamp collectors, they refer to themselves as philatelists or people who study stamps, buy used stamps. They are not likely to want to buy one or two stamps unless they are particularly valuable. People often buy big bundles or packages of stamps because they enjoy sorting through them and identifying them.
It depends on how organised you are
you can buy coupons at the post office that are redeemable in foreign countries for stamps
YES, although the denomination is different for US lettermail.