Problem:
The issue here is that the user wanted to disallow the deleting of posts if they are in a Post relationship.
Solution:
Unfortunately no this is not possible because even though the posts are linked they are still individual posts in themselves and can be deleted .
Problem: I would like to update to PHP 7 and upgrade to the new post relationships system. I have some custom code that may need to be updated.
Solution: Make sure the cred_save_data hooks are formatted with all 4 parameters when necessary. The other code looks okay as long as you do not re-generate Forms code.
Problem:
With a post relationship between two post types, how to display a field from one post when viewing the other post.
Solution:
If there is just one connected post then when inserting a field using the Fields and Views button you will see a Post selection tab, where you can specify which post should be the source of the field, e.g. a related post.
If there may be more than one connected post, you would need to create a View to show posts related to the current one and add the field in the output section of the View.