- Does the ticker show a message to my friends when I join a specific closed group? What about the same for the people who follow me?
- If someone is a member of the same closed group, but not a friend of mine, will they see my posts and likes in that group in their ticker?
No, unless your friend also has joined that group it will not appear. A closed group isn't the same as a secret group however, it is possible via various methods to determine if you are a member of a closed group.
No, they will not see the likes in the ticker, they will see some of your activity in his/her news feed, since he/she has subscribed to that group. For example, if User X posts something the group, and you comment on that, User Y may or may not see this as an activity in his/her news feed.