I have a mobile application, I have AWS ec2 instance java springboot application.
I want to know if I can implement Auth0 passwordless login with my backend services without my mobile app using the passwordless sdk. If so this will be great because then I can implement auth0 on backend side then use my own backend APIs as a middle man with Auth0.
In addition, in an embedded login situation you would be able to do it from the client application or your own backend (Passwordless Authentication with Embedded Login) so the answer would be: yes, your scenario is feasible.
Having said that, this will translate in you having public endpoints on your own system (they need to be called before authentication) which in turn will then call Auth0 endpoints from the backend so it will be your responsibility to ensure that your public endpoints are implemented adequately (rate limits, etc).