1. If they had tried their best, they would have succeeded in the interview. (subjunctive mood)

2. As they didn't do their best, they didn't succeed in the interview.
3. As they didn't do their best, they wouldn't succeed in the interview.
4. As they didn't do their best, they couldn't succeed in the interview.

#2, 3 and 4 are in the indicative mood.
What is the same as the Sentence among Sentence 2, Sentence 3, and Sentence 4?

Your indications of subjunctive and indicative moods are correct, as are the tenses.

I don't understand your question, though. "What is the same as the Sentence among Sentence 2, Sentence 3, and Sentence 4?" What is "the Sentence"?

??

There are two things that are identical. The introductory adverb clause is identical. In addition the verb in each of those three sentences is in the indicative mood.

1. If they had tried their best, they would have succeeded in the interview. (subjunctive mood)

2. As they didn't do their best, they didn't succeed in the interview.
3. As they didn't do their best, they wouldn't succeed in the interview.
4. As they didn't do their best, they couldn't succeed in the interview.

#2, 3 and 4 are in the indicative mood.
What is the same as Sentence 1 among Sentence 2, Sentence 3, and Sentence 4?

The sentence that is the same as Sentence 1 among Sentence 2, Sentence 3, and Sentence 4 is Sentence 4: "As they didn't do their best, they couldn't succeed in the interview."

Both Sentence 1 and Sentence 4 convey the idea that their failure to do their best resulted in their inability to succeed in the interview. They share the same cause-and-effect relationship. However, while Sentence 1 is in the subjunctive mood, Sentence 4 is in the indicative mood.