It is always a good idea to check how your form changes will appear for the form user before publishing live.
This is easy to do as you work through your form in the Funnel Forms Editor.
When working on your form in Editor mode, select the Preview mode button at the top of the page.
Once in the preview mode you can move through the form by either selecting on the pages in the left panel or select the next button on each page. The preview mode skips any validations so you can progress through the form without entering data.
Also in the preview mode is the option to view your form on either desktop or mobile view using the icons on the far right of the screen.