For more info on QueryBuilder, see Scott's Digital Community: [Webinar | February ] Ask the AEM Community Expert: Best practice to query JCR data using Que…

Look here. Using the CRX2Oak Migration Tool

You can look at writing a JCR event handler. When child page is created, the event handler can fire and add a prop to meet your requirement.

Typically components added to an editable template cannot be deleted by an author. Do not put in components into a responsive grid at the editable template level. Should be placed in the page level to let authors add/delete a component.

Follow this Helpx article. Adobe Experience Manager Help | Querying Adobe Experience Manager 6.4 JCR data using the QueryBuilder APIas you can see in video, it works fine.

You can also remove auth requirements so your 3rd party app can successfully invoke it.

Great response Arun!

Thank you for clarifying this!

I am not aware of any way to customize the widgets available with a content fragment model. I will check internally to see if anyone has thoughts on this.

I am not aware of any other way.