I never do this before <some event>. You are talking about possible situations or events. You would never perform some act before this event. "I never exercise hard just before a big meal." I never done this before - incorrect. It should be "I have (or I've) never done this before. You are about to do something now or could possible do it, or are doing it now, but you have never done it before. "This is the first time I've gone on a cruise. I've never done this before" "I never did this before" - actually, you would hear this in the same situations that you use "I've never done..." However, you would usually use this form after you have completed the act, rather than just before or during it. "That was a fun flight. I never did that before. It was my first flight."

do is related to present time so if you r speaking about the past , you couldnt use the word "do".but u can tell in this way . i never do this job for you(means that now at this time i dont do this) or it is never done before(((u can make passive sentence like that)))) or i / they never has / have done this before(( past perfect)) or speaking about past for yourself that u did and finished at that time you will tell: i never did this before.( means the time of doing sth is totally finished and now u r in another time ) i hope u can get ur answer from these statement. although u can ask about it privetly too , if u had some more question about it.