Hong Kong Airport to Harbour Hotel at Mongkok

Hi, our Cathay Pacific plane will arrive HK at 3.00pm and staying at the Harbour Hotel at Mongkok.
1. May I know the cheapest way to get to the hotel from the airport? Are we eligible to use the free shuttle bus by any chance?
2. Is there Free In-town Check-in Service for Cathay Pacific ?
3. What is the cheapest way to go to the airport from Harbour Hotel at Mongkok, my flight from HK is 3.00pm ?
Thank you in advanced for your help.