1. If I defriend someone, will they know it?

2. If a group were formed so they can post to each other and
You're not one of them, can you still get the posts. They
Kept their name and profile on FB. How is that done?
3. Can anyone form a group?

1. No
2. Depends on the group settings.

Public - Yes
Closed - No
Secret - No

3. Yes

Actually, if you defriend a person, they can indeed know. They will see that you two are no longer friends. Also, some addons for web browsers will save a list of your friends and notify you when someone goes missing from that list.

While a message is not sent about the "defriend" if they look at their list of friends, you will no longer be on it.

Now would you like to discuss the issues going on ?