@prashanthij - There doesn't seem to be any way to create a Bot using Bot Rest API using Teams developer portal.
You can create a bot with the Bot Connector service with the Bot Connector API.
Ref Documents:
https://learn.microsoft.com/en-us/azure/bot-service/rest-api/bot-framework-rest-connector-quickstart?view=azure-bot-service-4.0
https://learn.microsoft.com/en-us/azure/bot-service/rest-api/bot-framework-rest-connector-api-reference?view=azure-bot-service-4.0