Business Transaction functionality is not available in Dynatrace. You can use Key Requests in Dynatrace which will work in similar way as of your BT and it'll baseline those key requests URL automatically. You can see more details in the below link,
This is a misunderstanding, most of all functionality is available. Please see my first comment.
The most interesting parts are probably
* Request Naming which is most akin to BT and BT splitting: https://www.dynatrace.com/support/help/server-side-services/request-attributes/how-can-i-name-my-requests-based-on-request-attributes/
* Multi dimensional analysis: https://www.dynatrace.com/support/help/server-side-services/request-attributes/how-do-i-chart-custom-metrics-and-dimensions-based-on-request-attributes/
* Custom Business Errors: https://www.dynatrace.com/support/help/server-side-services/request-attributes/how-do-i-use-request-attributes-to-set-up-functional-error-detection/