How to make iframe think that it works inside the VK application?

Question

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There is a VK application.
I just open the address of his frame in a separate tab.
In fact, the frame address is a web page on the application developer's website.
So, when you open the address of the frame in the window, the frame says that it is not running inside the VK application.

How to make the page on the developer's server think that it is inside the VK application?

Answer 1

By analogy with https://github.com/sberdevices/assistant-client
In your case, I think it will be easier. It is necessary to emulate only the js vk api available from the side.
Probably still the user agent of a browser.