can user use mobile app to fill up the form?

We have mobile apps. Those Mobile apps are intended for administration of your Jotform account, forms and submissions. But not the actual filling of the form. I am afraid you cannot use them to fill out the form.

I would suggest you to make your form Mobile responsive, so your user can easily fill the forms on Mobile. Here is the guide, to make your form Mobile responsive: https://www.jotform.com/help/311-How-to-make-forms-mobile-responsive

If you have any query, or need further assistance, feel free to revert back.

Thanks.