Explanation:

Box 1: Yes
Only if you would like to share your connector with all users of Logic Apps, Microsoft Flow, and PowerApps, you can submit your connector for Microsoft certification. Microsoft will review your connector.
Box 2: Yes
Connectors created in Microsoft Flow are available in PowerApps. Likewise, connectors created in PowerApps are available in Microsoft Flow.
Box 3: No
If you would like to share your connector with all users of Logic Apps, Microsoft Flow, and PowerApps, you can submit your connector for Microsoft certification. Microsoft will review your connector.
Reference:
https://docs.microsoft.com/en-us/connectors/custom-connectors/