Regulation for rewring back box?

Thank you both for caring about my health and safety so much. Really appreciate it. So far, I still find this matter is under my comfort zoom.

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I have a degree in EEE, so it's not hard for me to understand the theory side of things. And combine information from different sources.

Thanks to @mapj1, I have read all the wiring information from the Flameport website, include how muti-way switches are normally wired. www.flameport.com/.../lighting_circuits_diagrams.cs4

The part that I'm concerned about is compliance and practical convention. I want to avoid making unstandardized wiring/hack and leaving the fellow electrician wondering what is going on and risk their safety.

I will of course not touch any of the wirings until I'm sure how they work and what I need to do.

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To address the concern, below are my current understanding and thought process:

I understand the image from flameport website does not have a real natural wire. And in the post above, the natural wire is "borrowed" as an output of the switch, which is actually live.

The picture of the back box I posted is a 1-way switch, with a loop at the switch. So the two of the incoming T&E wire are from the source and to the next switch (with their live connected to common), and the other wire is connected to the light bulb. All the natural and earth wires are connected, which confirms that no borrow exist. (Like the image below)

What I'm trying to say in the previous post is two fold. 
The first fold is given the figure as it is, would it be legal to convert it to one-way by abanded the wires in the latter two back box?
The second fold is if I have access to the neutral wire, which I need to check tomorrow. Then can I also safely terminate it in the first back box.
And for both termination/abandon what marking do I need?

I will of course come to it tomorrow with the actual wiring in my home, to be more certain of the setup I need to work with.

Thank you both for caring about my health and safety so much. Really appreciate it. So far, I still find this matter is under my comfort zoom.

-----

I have a degree in EEE, so it's not hard for me to understand the theory side of things. And combine information from different sources.

Thanks to @mapj1, I have read all the wiring information from the Flameport website, include how muti-way switches are normally wired. www.flameport.com/.../lighting_circuits_diagrams.cs4

The part that I'm concerned about is compliance and practical convention. I want to avoid making unstandardized wiring/hack and leaving the fellow electrician wondering what is going on and risk their safety.

I will of course not touch any of the wirings until I'm sure how they work and what I need to do.

-----

To address the concern, below are my current understanding and thought process:

I understand the image from flameport website does not have a real natural wire. And in the post above, the natural wire is "borrowed" as an output of the switch, which is actually live.

The picture of the back box I posted is a 1-way switch, with a loop at the switch. So the two of the incoming T&E wire are from the source and to the next switch (with their live connected to common), and the other wire is connected to the light bulb. All the natural and earth wires are connected, which confirms that no borrow exist. (Like the image below)

What I'm trying to say in the previous post is two fold. 
The first fold is given the figure as it is, would it be legal to convert it to one-way by abanded the wires in the latter two back box?
The second fold is if I have access to the neutral wire, which I need to check tomorrow. Then can I also safely terminate it in the first back box.
And for both termination/abandon what marking do I need?

I will of course come to it tomorrow with the actual wiring in my home, to be more certain of the setup I need to work with.