Friendly English Question

Factual Questions
1

This debate centers on the word “friendly” and its parts of speech. I submit the following four examples:

  1. Michael is a friendly person.
  2. This page is not printer-friendly.
  3. Marc is a friendly to our cause.
  4. Drive safely.

About which I say the following things:

  1. Adjective case, and most common in everyday use.
  2. Adjective case; decidedly informal.
  3. Noun case; also informal.
  4. Adverb case???

The OED lists one part of speech: adjective (please double-check this if you can). Some other dictionaries list the informal noun case, as well as an adverb case (Webster’s gives the example “friendly disposed”). Others mention “friendlily” as adverb form.

My questions are: (a) Is “friendlily” a word? If so, is it still used? (b) Can “friendly” be used as an adverb, such as in Example 4? If so, is this an informal or formal use?

Any help will be greatly appreciated.

2

Oops. In Example 4, of course, I meant “Drive friendly.”

3

I’m not an expert on grammatical nomenclature, but I would say:
a) “friendlily” and “friendily” are not words in English
b) example 4 could not use “friendly”, “friendily”, etc. However, you could say “Drive in a friendly manner.”

4

The more I think about it, I suppose it COULD be possible for someone to say “Drive friendly,” but most people would say it’s not correct, so I’d say that at best it’s very colloquial or dialect.

Most people would instead say “Be a friendly driver” or something like that.