1) You can choose to share a folder with a group. If you want to share a folder with 1 friend, you will need to create a group for this friend.
Then select your folder and right-click “Modify shared folder” button to restrict access.

2) To select 1 folder to share with a friend (a group) you just need to “share new folder” and restrict access like explained before. Then exclude this subfolder by modify the main folder.

Hope it can help.

1) In Giga 2.52 I could choose which contacts could access which folders so I could develop a tier sharing system.

2) I wanted to only select 1 folder with a friend yet when I unselected the parent folder and tried to select that one subfolder, all the other subfolders were selected as well.