Actually, This forum is related to the issues of the Pro theme, the forum for the free theme is located at the following address: https://wordpress.org/support/theme/agama/
Anyway … I will try to help you.
If I understand you well, you would want to have a full (uncropped) feature image in a Single blog post. If this is the case, follow the steps below:
Go to Customizing ▸ Blog ▸ Single Post
and turn off the Featured image on the single post.
Then upload the same image as your featured image, in the post content, and set the size and alignment as you wish.
Maybe the next video will help you with that.
Working with images
We prepare an update for the Pro theme in which we will add an option to turn off the auto-cropping for the featured images.