2) The array is an array of related post IDs and does not store the title of the post.
It is impossible to search for a title and get posts that have a relationship with another post with searched title. To do this the title of the related post would need to be stored in a meta field of the post where the relationship exists.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users