Really close and some good answers to your question! This one is probably debatable, but this is actually a conditional sentence -- the conditional clause "he had cared" should be preceded by the conditional "if". You could say, "He would have answered the phone if he had really cared." Or, if you were speaking this phrase, you probably want to emphasize the conditional clause (the 'if he had really cared' part), thus you could say "If he had really cared, he would have answered the phone." (this second version is the most likely way it would be spoken by a native speaker). Hope this helps.

The pattern you need is "would + have + [past participle]". In your example you added two past participles, and we can't tell whether you wanted "had" to be a main verb (possess, own, eat/drink?, experience) or an auxiliary verb. In the pattern "would have had", it's a main verb. ""He would have answered the phone..." is the correct phrase.

Good try, but the correct sentence would be: He would have answered the phone, had he really cared. OR He would have answered the phone if he really cared.

I would say "He would have answered the phone if he really cared" "would have had" doesn't work quite right in this case Keep it up!