First off, the point of prepared statements and escaping is to separate the data from the surrounding language context and prevent syntax conflicts. If you don't know what that means, try to insert "O'Reilly" into a single-quoted SQL string.
This has nothing to do with "attacks". It's not an "attack" to be named O'Reilly. The problem here is a software defect caused by naive programming.
Of course prepared statements can also prevent attacks. But the primary goal is code correctness -- the fact that correct software happens to be more robust against attacks is a nice side effect.
Secondly, assuming that values from the database are somehow inherently secure is wrong and can leave your application wide open to second-order injections. You shouldn't make any assumptions about whether or not a value is "secure". a) you're missing the point (see above), b) your assessment may very well be wrong (attackers often have a lot more fantasy than the average PHP programmer) and c) constantly switching between escaped and unescaped values will sooner or later lead to a mistake.
The correct approach is to always use parameters, unless the string is explicitly supposed to contain an SQL fragment.
This is true for every language, not just SQL. It's the same with HTML, XML, shell commands etc.
If you read any books about teaching, coaching, etc you have to win the trust of your student before they will listen to you.
Your learning theories are bullshit.
The truth is that you haven't made any significant progress. Several very knowledgeable users have spent a lot of time explaining the same basics over and over again, and they've been exceptionally patient and friendly. None of this has helped. You've either simply ignored them or come up with all kinds of reasons for why their advice isn't relevant.
So how about you stop blaming everybody else and realize that the problem is you. PHP isn't rocket science. Somebody who already has prior programming experience can definitely learn to write decent code in a few weeks. However, learning requires motivation and the willingness to shut up and listen. You don't have that. Whenever somebody points out a mistake, you make it anyway. Whenever you get important information, you brush it off, assuming that you somehow know better.
With that attitude, you may be able to produce code. But you won't learn how to program.