To start a dissertation presentation you need to restate your research question. Then, show how your research outcomes answer the research question. Show your contribution to the research and state its limitations as well. Finally, suggest future research and recommend any more possibilities. This is how you start and end your dissertation presentation.
It depends. It can even go for two hours long or an hour and a half. Mostly it is based on the discussion and its quality between students and his/her examiner and research supervisor. However, a dissertation is way shorter than to write a dissertation.
A dissertation presentation is the assessment of your complete dissertation. It is held to identify your research and its purpose and how well you defend it. Dissertation presentation shows your command over your research. For a mid-research presentation, students are given an opportunity to demonstrate their progress.