Youtube Self-Promotion

Hi! I have 2 technical questions regarding to self-promotion on Youtube Channel:

  1. Can I publish my VH preview videos in higher resolution than on Videohive site, particularly in Full HD resolution? I saw people doing this but it were AfterEffect Projects.
  2. And the second one, if Ill stress that the movie is Videohives property and Ill put proper links to VH site, do I have to put Videohive Watermarks in these videos?