I can see that three people have already answered the question, namely, Stephanie, Maidhc, and Caprine20. Someone has given a thumbs down (-1) to all three answers. It is not fair to give a thumbs done to someone who has taken the time and made the effort to help answer a question, unless the answer is stupid, disrespectful or 100% incorrect. Each of the three answers are reasonable and nearly perfect, so I'm going to give a thumbs up to each of the responses. Besides, the person who gave a thumbs down probably didn't even try to answer the question.
Mitong wrote: 2) I've never seen it before. I think they call the 2nd "past perfect."
[THE VERB "HAVE SEEN" IN THE 2ND SENTENCE IS THE PRESENT PERFECT TENSE. The Past Perfect = "had seen".]
MY ANSWER TO LIANA'S QUESTION "What's the difference between "never seen/saw it before"??
When we think or speak about a period of time that started in the past and continues up to the present we usually use adverbs that refer to an indefinite (not specific) period of time, such as: ever, never, before, yet, and already.
In these cases we use the Present Perfect tense = present tense of the auxilary verb/helping verb (have/has) + the past particle of the main verb (seen).
Have you ever seen a ghost? No, I have never seen a ghost?
I'm sure we have seen this movie before? He has not seen this video yet.
Have you already seen this video?
But when we write or speak about a more definite period of time, such as, today, yesterday, this week, this past month, last year - we usually prefer to use a simple past tense because it sounds better, for example:
I saw a ghost last night/last year.
I saw this movie last Friday.
He saw this video the last time we were together.
NOTICE that all the definite period of time examples above are in affirmative sentences (positive statements, not questions and not negative statements). The words that describe the event's time or activity are definite (one specific time).