> I believe the OP should write down all their questions in a structured format, and then schedule a meetings with 1 person helping them onboard, ...

Let me guess: that 1 person will of course not be you, right? Because if it is you, I bet you will complain even more.

Also, it's ridiculous to pretend that all questions require deep dive at length. Some do, and, yes, I agree we should do that for those. But what about the majority of the questions? If these questions still exist, then you will still be interrupted, so it will not solve the situation.

Also, it is quite telling that you did not also consider another solution: if they need to ask you a question, you could have avoided that by properly sharing the information before hand. But of course, it's always someone else's fault. (just to be clear: it is sometimes someone else's fault, but your way of reacting of just thinking that everyone else should adapt is just giving me the impression that you don't care about solving the problem in a fair way)

But it does not answer my question: what you ask them to do is very inconvenient and inefficient, as the large majority of questions do not correspond to big dangerous lack of knowledge that needs 3 hours lecture course to be solved. So we still have the problem: why should the company pay for one person being less efficient because of needing to do all this useless process, instead of paying for you being less efficient?

> I do put noise suppression headphones, but they can't stop the people moving in front of me ...

As I've said, I don't understand how people can be in "deep flow" and be so easily distracted by people moving around. People are different, so I can understand it can be a problem for you. But my problem with this reaction is that everything is centered around what is best for you, without any considerations of how it affects others. I reacted because you first mentioned that GP was behaving like a toddler, but in your reaction and the description of the problem, you seems to focus on you, you, you, which does not look very grown-up either, don't you think?

> ... nor the taps on my shoulder

If they tap on your shoulder, you should simply answer, like a grown-up does.

> Not wanting to be interrupted is not forcing others to take care of your needs.If you are unsure what I mean, let me call you in the middle of the night ...

But you are not complaining about being interrupted in the middle of the night to talk about things that is not related to you, you are complaining about doing your job: working with colleagues and sharing information so that they can progress.

What I'm saying is simple:
1) you can be a toddler and interrupt someone constantly for no good reason. This is not good and unprofessional
2) you can be a toddler and cry when someone interrupt you for a good reason. This is not good and unprofessional
3) the good situation is in the middle: you WILL have some level of interruption, it is just unreasonable to expect otherwise and it is childish to ask people to jump through hoops to care to your need to never be interrupted.

> How dare you forcing me to have normal boundaries and call you at reasonable times!

You don't have normal boundaries. Grown-ups at work know that they will interact with other people. You inventing that people should not interact with you, or interact only in your own terms even when it is inconvenient for them.

> Hence me liking the OP's behavior to that of a toddler.

OP's behavior did not even mention if they interrupt people that have inform them they don't want to be interrupted.
As far as we know, OP's behavior is 100% compatible with what you want.