Can I buy multiple Tourist Day Passes

I am staying in Hong Kong for 10 days. Just HK, not mainland China.
1. Can I buy THREE Hong Kong MTR Tourist 3-Day Passes?
2. If not, can I buy ONE 3-Day pass and multiple 1 day tourist pass for each day of my stay?
3. Can I buy both 1 day and 3 day tourist passes at HK Airport or I have to purchase online?

Thanks for your help.