Little Recordings
The alter ego of Kristen Is Calm- Kristen is Angry
@francisleo summed it nicely. Be sure to make it crystal clear that "this is part 1/preview/whatever", since there is nothing more annoying that those "ou yeah here is a full video, ou wait it is not, give me MONEY!". So dont be that, pleaseNo that is not possible, I think you can set a certain time that the video will start and end if you play them through a playlist but the user can still see the rest of the video if he wants and the rest of the video isn't hidden from the user at all. It is simply skipped and when you hit the end point you are sent to the next video.
The Youtube editor will only let you create a new video unfortunately and deleting and reuploading will make you lose all the views/likes etc. you got on that video.[DOUBLEPOST=1397165717,1397165552][/DOUBLEPOST]Actually @Little Recordings makes a good point, you can just upload the first part as a trailer (although I'd advise you make it shorter if you want to call it a trailer for a video only double it's length) and then at the end of the trailer say when the video will release. It will also look a lot more professional and really make people eager to see the video.

I have seen that method done by a lot of people, having unlisted videos going from preview videos, so it is a legit way : )
Glad I was able to lend a hand, by accident

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I think I found another way around this but I still have a lot of time before actually doing this so yeah.