You can create a Tenant or Developer account using FREE Office 365 Subscription< under the Office 365 Developer Program, once created you can use the Tenant and create accounts in that Tenant and provide necessary permissions /configuration from your side so that we can test the app.
As discussed, please provide the configuration document/help document and sign up link within the Welcome message & help response for the new users to use the app without any issues.
Help command should provide value proposition of the app to the users in the bot.
As discussed, please share the complete test instructions for us to test the end to end functionality of the app.