What'a the difference between this lesson and a previous one

Question

HolaI'm confused as to why this lesson exists. Doesn't this one Using se debe/n and se puede/n + infinitive to say you must / you can (passive) already cover it??thanks

Answer

Hola Pippy
They are very similar but not talking exactly about the same thing.
One lesson is about using "Se debe/se puede +infinitive". Here you only use these forms in the 3rd person singular (debe/puede) and they are used with intransitive verbs (no direct objects):
Aquí en este restaurante se puede fumar. Here in this restaurant one can smoke.
The other lesson using "Se debe/se deben/se puede/se pueden + infinitive" is about a form of Passive sentence. It is like when you say "En este bar se sirven paellas todos los domingos" (In this bar paellas are served every Sunday), but with modal verbs deber or poder, for example:

En este bar no se pueden beber bebidas alcohólicas.
In this bar alcoholic drinks cannot be drunk.

You need to make the modal verb poder agree with "bebidas alcohólicas" (plural noun) -> se pueden
These structures are very similar and sometimes they are actually translated the same in English, but in Spanish they are either impersonal sentences or passive sentences and the important part is the agreement, as explained before.
I hope this clarified it for you
Saludos
Inma

Answer

Would it also be correct to say, "En este bar no se puede beber" because now it would be it would be impersonal? But it would be incorrect to say, "En este bar no se puede beber bebidas alcohólicas," because the verb is no longer intransitive?