Thanks for reaching out.
Please find below my replies to all your questions:
Yes, it is correct behavior. Placeholder - default text description that will be displayed in the editor until there is something to preview. So it could not be changed depending on some criteria dynamically.
Initial Value - file to be uploaded to AWS initially, when the page with the plugin loads (it is an optional feature). Dynamic-link will be uploaded to AWS initially:
Please share the settings for this field, so I will be able to check if all is configured correctly.
Please make sure that you have configured this action properly. Place a button on the page and give it a name (for example, ‘Delete Files’).
Here is the example of the correct settings from our demo page:
Looking to hearing from you soon.