How to design a responsive spa app?

Question

Angular

Question about layout and routing. Mobile application screens are smaller in capacity, therefore there are more screens. In the desktop version, the situation is reversed. Consequently, the handlers are also different: in one case, this is a transition to a new screen, in the other, opening a modal window. Does this mean that adaptive layout is not applicable for applications and you will have to make different views on different devices? Or is it still possible to competently build adaptive applications? It is desirable to use dynamic loading of modules in this case.
I use Angular, I'm starting to learn Ionic.

Answer 1

Does this mean that adaptive layout is not applicable for applications and you will have to make different views on different devices

The point of responsive layout is that the content adapts to the screen size. Your cap :) In the above example, there are no contradictions with the principles of adaptation
This can be implemented within the application. Here is an example of react and react-router v4: https://reacttraining.com/react-router/web/example... . There, the images in the gallery open either on the page or in a modal window. Depending on how the page was opened (note that the url of the gallery elements is the same in different ways of displaying)
Yes, you can. But you need to think through all the moments in advance
This allows you to optimize performance (initial render time, amount of data / code transferred, script parsing time, and so on). If you need it - use it)

Answer 2

The ideology of the components is precisely that one component would be described so that it could be reused in several places. Thanks to this, you do not copy a bunch of code 500 times in different places.
As for adaptability, there are a bunch of different grids that allow you to layout without fear for adaptability.
Examples: bootstrap or material ui

Answer 3

If the screens are very different, I would suggest making 2 different applications, but with partially shared components (that look the same or almost the same). Otherwise, the complexity of layout can easily go beyond reasonable limits.