To create Bot please refer below document:
https://learn.microsoft.com/en-us/microsoftteams/platform/resources/bot-v3/bots-create
You can send proactive messages to the user.
A proactive message is any message sent by a bot that isn't in response to a request from a user. This message can include content, such as:
Welcome messages
Notifications
Scheduled messages
Thanks,
Nivedipa
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