The chat group feature on the imo for Android lets you get in touch with friends at one place. But if you want to delete and leave a group on imo, you need to do as follows:
1. Open the imo application on your Android device
2. Under the Chats tab, tap the group you want to leave/delete
3. Now, tap the group name on the top of the page to open the Group's Profile.
4. Tap the 3dot icon on the top right and simply touch the Leave option to leave a group on imo
** Note that, if you long press the group name from the Chat tab, and tap the Close chat option, it just closes the just and you will still get new messages from that group. If you have already closed a group, you need to move to the Contacts tab, tap the Group name and do the rest as specified to delete the group.