Comma rules help- please check for error!?

1. Correct
2. correct
3. correct
4. I had the pleasure of talking to a woman who had just returned from India, where she had lived for ten years. Omit the first comma because the phrase "who had just returned from India" is restrictive. Keep the second one because "where she had lived for ten years" is nonrestrictive.
5. Patrick’s oldest sister, Fiona, graduated from MIT with a degree in aerospace engineering. Patrick has only one oldest sister, so "Fiona" is an appositive and should be set off by commas. It takes a pair of commas to set off a word or phrase within a sentence.

Edited to add: For some years, many English teachers taught that in a series, the final comma before the coordinating conjunction could be omitted. The source of approval for the omission was journalistic preference (not including the final comma saved lead when newspapers were printed from lead type) and literary acceptance. In all other cases, such as business usage, the final comma is required. It is also required in any situation where misreading could result from its omission (but journalistic style omits it anyway, causing occasional unintended humor or confusion in newspapers). Most authorities (such as Strunk & White and The Gregg Reference Manual) recommend including the final comma. Today, most teachers of writing mechanics teach that it should be included, primarily because it's easier to teach that it should be used than it is to teach how to tell when it can be omitted in literary writing.

1 is fine. When you list, you don't need the comma before and. so it could also be "We prefer our staff to be orderly, prompt and efficient. I think (not 100 percent) that in the US, you don't put the comma, and it the UK, you do.
2 is fine
3 fine
4 wrong. It should be "I had the pleasure of talking to a woman who had just returned from India, where she had lived for ten years." 'woman' does not properly identify the person, so you don't need a comma.
5 wrong. it should be "Patrick's oldest sister, Fiona, graduated from MIT with a degree in aerospace engineering." You interrupted the sentence with her name, so you have to surround it with commas.

Hi, Refine J!

As a general rule there are two main places that you use commas - and they are to make it easier for the reader.
When you have a series of things or adjectives and you put commas between them all except the last two which get an "and".
When you have two things side by side that refer to the same thing, which is called "in apposition."

I would do yours like this -

(1) We prefer our staff to be orderly, prompt and efficient.
series of things or adjectives

2) For breakfast, the children ordered corn flakes, English muffins with peanut butter, and Cherry Cokes.
This one is tricky because, if you leave out the last comma, you totally change the meaning. I would write it as you have.

3)Choreographer Alvin Ailey’s best-known work, Revelations, is more than just a crowd pleaser.
two things side by side that refer to the same thing
best-known work and Revelations

4) I had the pleasure of talking to a woman who had just returned from India, where she had lived for ten years.
India and where she had lived refer to the same thing.

5)Patrick’s oldest sister, Fiona, graduated from MIT with a degree in aerospace engineering.
sister and Fiona are the same thing