Questions:
1: Many articles will tell you not to say "I don't know"; however, I have read just the opposite in many other articles. I do think the main point of those articles (and any really) is don't just make up an answer if you don't know. Either tell the audience member something like "Great question, I'll get back to you on that" (and then do get back to them) or you can use the approach you mentioned in the video about saying "In my opinion..." I think both are acceptable.
2:After watching this video, I found that the speaker was spot on when he said understanding your material. I always feel much better going into a presentation when I have a better grasp of the material. I found myself having the ability to really go much deeper in depth and I can also see how the audience responds to it as well. In my mind this creates a certain energy that can really help with the participation of the audience. Once you get that I think you can call the presentation a success as they are now showing that they too are invested in the material.
3: Describe the tasks in presentation development. Find examples of what not to do and explain why. ?
4: The planning portion is the foundation for a successful presentation. Allowing ample time to research the subject is also a very important task, by doing this is you can take the time to now be a subject matter expert. This will only help you when presenting, also keeping in mind your audience and who will be present is helpful. This will help determine what kind of presentation you will be creating. One of the examples that I have to remind myself when presenting is to slow down when presenting. Being in sales and always on the go I have to take a deep breath and remind myself that the audience is the most important part. As I'm trying to both inform and persuade at the same time.