We are new to SAIL, Could you please let me know if a SAIL form can be used for

Yes, you can very well use SAIL in the portal based process models.

Thanks Umesh, Could you please share some links where I can find more details on this? When I configured SAIL from in the properties of user input task, it gave me a message "The form can be viewed in Tempo" while running the process and routed me to the tempo suite.

Hi,
SAIL based task forms (or rules) work on the Tempo interface across several supported browsers and on mobile devices. As far as I know, the SAIL based forms are not built to work on portal (apps) interface. You can read more on this here - forum.appian.com/.../SAIL_Design

Yes Navajith, it will only open in the tempo. Usually, we create a task for user/user's which will be visible in 'Tempo Tasks' and from which assinged user accept it and execute it.