pat {L_WROTE}:
1) The hostel will be at yung shu wna... and i like hiking... is it worth to walk from yung shu wan to sok kwu wan and have seafood dinner there ? and then walk back to yung shu wan, will it be too dark to walk after dinner ?
It's a wide concrete path. Take a torch and you'll be fine.
pat {L_WROTE}:
2) And any possibility to ride bicycle from sok kwu wan to yung shu wan, or riding around lamma?
Yes, that's common. Because Lamma is not a Country Park, you can ride cross-country too. It's steep, and look out for tourists on the main path.