Please find Settings->About phone->Build number, click the build number 6 times continuously, it will turn the device into development mode, and you will find Settings->System-> Developer options is there, if any other questions let us know,thanks.
Yes, we can add a password before enter the Settings menu to restrict user access,if you accept this way, please let us know the password, thanks.
Yes, you can use external PIN PAD with F20 device.Currently we have no specific external PIN PAD devices in our side, so if you are
using external PIN PAD devices in your side, please let us know the type, we can check if it can work normal in our devices.
Attached is the description document, please check it, if any question let us know,thanks a lot.
We will provide STORM training for you, there are the STORM training document and vedio for your reference first.