Here is a solution to address each of these problems.
Download a YouTube video
Yes you can download a YouTube video to save for as long as you would like. In your internet browser, before the word "youtube" type the letters "ss". It should look like it is below:
Press "Enter" and you will be prompted to save the YouTube video. It is that simple.
Get rid of annotations
Annotation can distract the viewer of a YouTube video and possibly ruin a good teachable moment. To get ride of annotations, select YouTube video you want, then copy the letters and numbers after youtube.com/. This is the unique code for the YouTube video. Then type "www.quietyoutube.com" and paste the unique code afterwards. It should look like it is below: