How to know total height of the form

3. Moreover, how to clarify the total height of the form?

Hello,

This could be tricky as the height is dynamically calculated based on your form's fields.
But you can check the current height of your form by looking to the iframe code.

On the form editor screen, go to Setup & Embed and click on the Embed Form icon.

Then click on the iframe option.

And you should be able to see the current height of your form on the displayed iframe code

Please let us know if you have further questions.
Thank you.