In answer to your questions:
Yes our themes are compatible with a WordPress multi-site setup.
I'm not aware of any specific issues with this, it shouldn't be a problem though.
This is not a default feature of the theme to allow a free period before changing to a paid listing, but you can offer a free short term listing period using listing plans.
There are no settings for this specifically.
Yes, we certainly recommend that if you're planning to make changes to the default theme that you create a child theme as it will not effect core functionality.
Yes, you can disable events via a setting within the themes admin dashboard.
There is no setting for this, it would require customization on your part.
No.
Yes you can upgrade later if you wish.
The Directory child theme is not created by AppThemes, but all information about it is on the
products marketplace page and you can use the "Comments" tab if you wish to communicate with the child theme developer regarding those related questions. Thanks.