Spelling "means" or "mean"

Question

I came across "means" in my studies. Here is excerpt out of my business course book.

For a fax the same rules apply as for a business letter, "only the means of communication is different".

means @ Cambridge Dict.

"means" is singular here but a plural noun used with "is different"

Question 1: Do we see "means" always in singular in such context or others ?

Question 2: Would be "only the meanings of communication are different" similar to the use of "the means of communication" ?

Question 3: Can we use "only the mean of communication is different"? Singular

Cambridge Dict. says here: Even though it ends in an ‘s’, means is a singular noun. We use a singular verb with it. We use it to talk about a method of doing something:

The most economical means of travelling to Aberdeen is by plane. (the most economical method or way)

Not: … most economical mean … or … most economical means are …

Answer 1

1. Yes, means is always singular when it's used to mean "a (single) method" or "a (single) way of doing something". For example, "The best means of reaching the mountain is a horse-cart". You can use it as the plural when it represents multiple methods or ways, like "All three means of transport we use cost more with the increase in petrol prices." (Thanks to urnonav for pointing that out!)

   
   Be careful, because means can have other meanings, as in "I understand what he means (intends)" and "Live within your means (resources)" and "Find the means (averages) of the three sets of numbers."

2. Meanings is completely different and you can't use it as a replacement for means. Meanings means "purposes" or "intentions" or "what is meant by something".
3. No, you can't use means as the singular mean when you mean "a method or a way"; it's always means and yet you use a singular verb with it just like the Cambridge dictionary says.