Is there any demo?

Also while trying it out, I find that I get ‘Add Media’ button above the editor. But as an user with ‘author’ role I can not add media inside a post. It says “Sorry, you are not allowed to attach files to this post.”

Though ‘Upload Media’ button below the editor is ok.

Glad to help:

1) “Can I see any front end demo?”

Not at this time.

2) “Can multiple images be included inside the post?”

Yes there are settings to control min/max number of images.

3) “I get ‘Add Media’ button above the editor. But as an user with ‘author’ role I can not add media inside a post.

That is correct, the user needs to be an Editor role or better to upload images.

I hope this helps, let me know if I can provide any further infos.