Hi,
There are two different issues that we will respond to below!
A. Facebook APP ID
We removed the feature as it no longer has any relevance for Facebook. Even though the Facebook debugger tool asks for it, Facebook has silently removed support for it and they just need to update the debugger tool. You can see this Tweet from Joost mentioning this here: https://twitter.com/jdevalk/status/1342514679575416832.
B. when share post-default image is shared in the feature image
To clarify, you are expecting Facebook to show one image but a different one appears? If so, We would like some more information.
1. Can you provide a link that highlights the issue?
2. Can you let us know what image you are expecting Facebook to show? A link to it would be helpful.
3. Can you elaborate more on how you are assigning this image? Are you setting it as a featured image and expecting Facebook to use that?