La acreditación permite entrar en el salón del cómic.

No. In this context, acreditación means something like accreditation, authorization, badge, pass, or credential that allows access to an event.

It is not the same as English credit in the financial or academic sense.

At events in Spain, acreditación often refers to:

• a press pass
• a staff badge
• a professional pass
• some official document showing you are allowed in

Because acreditación is a singular feminine noun, so it normally takes the feminine singular article la.

• la acreditación
• la entrada
• la invitación

Spanish usually uses articles more often than English does, so where English might say Accreditation allows entry, Spanish naturally says La acreditación permite entrar.

Because the subject is la acreditación, which is singular.

• La acreditación permite... = singular subject → permite
• Las acreditaciones permiten... = plural subject → permiten

So the verb agrees with acreditación, not with entrar or anything later in the sentence.

Because after permitir, Spanish often uses an infinitive to say what someone is allowed to do.

Pattern:

• permitir + infinitive

So:

• permite entrar = allows entry / allows someone to enter
• permite pasar = allows someone to go in / pass
• permite acceder = allows access

This works like English allows + infinitive idea, although English often inserts an object:

• The pass allows you to enter Spanish can leave that you unstated if it is general:
• La acreditación permite entrar

It is not expressed, because Spanish often leaves it implicit when the meaning is general or obvious from context.

So La acreditación permite entrar literally feels like:

• The accreditation allows entering or more naturally:
• The pass allows you to enter
• The accreditation lets people in

If you wanted to make the person explicit, you could say:

• La acreditación te permite entrar = The pass allows you to enter
• La acreditación permite entrar a los asistentes autorizados = The accreditation allows authorized attendees to enter

In Spain Spanish, entrar en is very common and often preferred for to enter a place.

• entrar en el salón
• entrar en la sala
• entrar en el edificio

You may also hear entrar a in some regions, especially in much of Latin America, but for Spanish from Spain, entrar en is the safer choice.

So for a learner of Spain Spanish, entrar en el salón del cómic sounds very natural.

Here salón does not literally mean a living room. In Spain, salón can also mean a fair, expo, show, or large event, especially in names of public events.

So el salón del cómic is likely the name of a comic convention or comic fair.

Examples of this kind of use:

• Salón del Automóvil = motor show / car show
• Salón del Manga = manga convention
• Salón del Cómic = comic convention / comic fair

So this is probably talking about entry to a specific event.

Because del is the contraction of de + el.

• de + el = del

So:

• el salón del cómic literally means
• the hall/show of the comic but naturally:
• the comic convention
• the comic fair

You use del because cómic is masculine here:

• el cómic
• del cómic

Because in Spanish the word is normally written cómic, with the stress on the first syllable: CÓ-mic.

The written accent shows the correct stress pattern.

This is common when Spanish borrows a word and adapts it to Spanish spelling conventions. So even though the word comes from English, in Spanish it is treated as a normal Spanish noun:

• el cómic
• los cómics

It depends on whether you are using it as a generic description or as an official event title.

• Generic: el salón del cómic
  = the comic convention
• Official title: el Salón del Cómic
  = part of the formal name of the event

In your sentence, lowercase looks like a general description, unless the source is intentionally not using title capitalization.

Yes. That is also natural, but it is structured differently.

• La acreditación permite entrar en el salón del cómic. = The pass allows entry into the comic convention.
• La acreditación permite la entrada al salón del cómic. = The pass allows entry to the comic convention.

Both are correct. The version with entrar sounds a bit more verbal and direct. The version with la entrada is a bit more noun-based.

Because there is no direct object referring to a specific person.

The personal a is used before a specific human direct object:

• Veo a María.
• Invitaron a los periodistas.

But here:

• permite entrar uses an infinitive, and
• en el salón del cómic is a prepositional phrase showing place

So there is no need for the personal a.

It sounds neutral and fairly formal/informational. It would fit well in:

• an event website
• a notice
• instructions
• a ticketing or access policy

It does not sound slangy or especially casual. That is partly because of words like acreditación and the impersonal structure permite entrar.