Is it possible to use the same ad block, that is, the same code generated by the google-adsense application with a single ID , on different pages?
The idea is to modify afterwards, the size of the ad block in a common file CSS , where applying the responsive-design directives can be used to be displayed correctly on different devices.
Yes. You can refer to the same ID from different files CSS . Some will complement others or even overwrite each other if they are repeated (depending on the order in which the amounts in the HTML, those below will overwrite the first ones).
If you want to put more than one div with the same styles (ads) you would have to put a clase (which are represented with a . first in the CSS style sheet).