Hello, We are traveling to Hong Kong and staying in Kowloon side from May 5 - 10.

Obviously the best option is to purchase an Octopus card. I have some hazy details I would like to clear:
#1 - "Consecutive 3 days free MTR usage" ( meaning May 5-7 ) What happens on 8-9-10? I am asking this since we would of course use the airport express on the 10th to come back to HKG International. Can I sue the card? If so what do I have to do?
#2 - What is the cost of the card if we would like to use the AE into town on the 5 th and back to the airport on the 10th?
#3 - Can I use it to on the harbor ferry?

Basically during our stay we will be around the main touristic areas and sights, such as Tsim Sha Tsui, Mong Kong, Nathan Road, Victoria Peak, HGK central, Temple street market, Lady's market, Man Mo temple. Is there any restrictions around these areas? I read above there are some exceptions using MTR but those lines seems to be not around my planned destination. Can you help me here?

I appreciate your comments

Regards,

Gábor