Authenticate participants via SMS(without register in Echo Sign)

Hi.

I'm having issue with Adobe Sign.

I need follow flow worked:

1) The system upload document to Adobe Sign via API (it's done)

2) Anyone can see/sign uploaded document after Phone verification(SMS)
with Widget i have an error - "Phone authentication is not applicable for widget participant set info". Also to see the uploaded doc every new user in my system should be registered in Echo Sign. How to prevent it. Just verified by sms and sign the doc.

3) The system can download signed document.

Could you please explain in details how to get worked 2) and 3) via API

Thanks in advance.