How to enable to filli out the form later?

I need to know if after I send a link to someone to fill out a form they can:

A) Start filling it out

B) stop for a time, then come back later (to the same link?) and finish filling out the form then submit

Yes. It is possible to enable the users to continue filling the form at a later time. If you are using Classic forms, you may enable Auto-fill feature from the form settings.

https://www.jotform.com/help/227-How-to-Enable-Auto-Fill-on-Forms

This method stores the form data in the browser storage and can be accessed be only when the form is opened using the same browser and same PC. 

The other method Session parameter method works when you have multiple pages on the form and can be accessed from other PC or browser since the form data shall be stored as a session in JotForm servers. Please refer to the guide below:

https://www.jotform.com/help/97-How-to-Save-Forms-and-Continue-Later

If you are using Card forms, please refer to the form that either of the option can be enabled from the form settings.

https://www.jotform.com/help/495-Setting-up-the-Continue-Forms-Later-Feature-in-Card-Forms

Hope this information helps!