1. Can I interact with multiple team members at the same time using the chat?
Yes, you can talk with multiple team members using the collaboration channels.
2. When you get a message in the chat. Do you get a notification? How do I know I have a message?
Yes, you get an email notification and the collaboration tab will have a bubble showing how many messages you've got. Keep in mind that the email notifications can be perceived as spam and end in your spam folder.