How to allow users to continue filling the form on a later data and different devices?

OK - so if they start filling the form ou on their mobile device on the way to work then save it, then get to the office and enter the form again from their desktop, and then save it again and go home and enter the form on their laptop at home, they can just pick up where they left off on the form each time, or go back to a question if they want and can add more detail? 

Yes this will be possible to do, you need to use the save and continue later method, this way you will create a session and will allow your users to start filling the form and then continue filling it in a different device, the same example as you provided, it will be achieved with this method, but you should indicate that the link with the session variable should be saved and the same should be used in order to continue filling the same form, otherwise an empty form will be shown. 

Here is the link to the guide that will provide you with the steps to apply this feature to your form: How-to-Save-Forms-and-Continue-Later

If you have any other question, please let us know, we should be able to help you. 

Got it - thank you so much. Really appreciate your help.