Question

Select all that apply. Which of the following are correct? Daniel, that guy with the hair, is sitting at the end of the hall. Daniel (that guy with the hair) is sitting at the end of the hall. Daniel—that guy with the hair—is sitting at the end of the hall.

Answer 1

Grammatical Apposition is the the condition of being side by side; and those combinations of long or short words are called "appositives".

In grammar, apposition is a structure in which 2 components are set side by side, and 1 component names or identifies the other, such as when a word or noun is accompanied by a phrase or another noun that renames that noun or subject word.

If the appositive is not essential to the meaning of that noun, they are always separated by commas.

Thereby, the correct one would be: "Daniel, that guy with the hair, is sitting at the end of the hall".

Answer 2

I believe that the two sentences (apart from one with the brackets) are correct. So, those would be:
1. Daniel, that guy with the hair, is sitting at the end of the hall. 
2. Daniel—that guy with the hair—is sitting at the end of the hall.

Using commas and dashes to separate the appositive phrase from the rest of the sentence is grammatically acceptable, whereas using brackets is not.