You need to be fully onboarded to get access to API and Merchant panel
2.
Available Payment methods depend on your subscription plan and agreement.
3.
All endpoints you will find listed in our API Reference documentation.
To get access to test Credentials you need to log in to your my.zen.com panel, then select the Store settings and go to Settings page to check your individual Credentials.
In the control panel you have possibility to track your Transaction, create Refunds, manage you Shop settings etc… You can find there as well Credentials to your Shop / Terminal API.