Can I use one field input as the name?

can I use one field input as the name? for example, instead of "demo form", can it be named "John"... like using {name} or #input_01

Unfortunately, that's not possible in the form builder and will not probably be implemented for SEO reasons.

However, you can always implement that within the form source code. Here's How to get your Form Source Code

The script here will help https://www.c-sharpcorner.com/UploadFile/c63ec5/change-page-title-dynamically-and-clear-textbox-value-with-j/