Reply To: How to add custom notification while creatin new topic?
a. Stop All Notifications for this Topic
The user can just unsubscribe from the topic either from their profile or visiting the topic again.
b. Provide one Daily Notification with all Comments for this Topic
c. Provide one Weekly Notification with all Comments for this Topic
For a daily digest I guess you could use this plugin, but it might not be exactly what you are looking for, and users have reported the plugin not functioning properly. You may need to hire a developer for users to get a daily digest of a specific topic.