I'm learning. (base)
I'm learning how to do things. (adjective phrase)
I'm learning how to do things in a way. (adjective phrase)
I'm learning how to do things in a way that serves me. (adjective clause)
"a way that serves me." is the important part of the sentence.
"that" is a relative pronoun.
the antecedent for "that" is the adjacent noun, "a way".
When a verb has two or more subjects connected by or or nor, the verb should agree with the last-named subject. Thus,
...when one or two individuals do not have IDs
(You'll note that you already used the plural form of the verb, "do" in this example)
...this is the case when one or two students are missing.
According to the IEEE Style Guide (archive link here), under "Some Common Mistakes":
The word “data” is plural, not singular.
So if your formal context is an IEEE venue, the answer is authoritatively "plural."
Saint Vincent and the Grenadines is a multi island Anglo-Caribbean
country in the Lesser Antilles island arc...
Saint Kitts and Nevis is an island country in the West
The Archipelago of San Andrés, Providencia and Santa Catalina
is one of the departments of Colombia.
The Turks and Caicos Islands are a British Overseas Territory
"Most everyone" behaves the same as "everyone". "Everyone is always singular" is oversimplified.
As a subject, "everyone" and "most everyone" always take singular verb agreement in standard English, so "Most everyone gets..." is correct and *"Most everyone get" is incorrect.
As an antecedent, "everyone" can be coreferential with a plural pronoun, and other ...
“What you see and what you hear” is treated as singular, not plural here, as you can see from the use of the word “it” instead of “they” at the start of the following sentence. Therefore, there is no plural subject.