I will do this epic book trailer promo

if your text exceed the space available, it will force me to reduce the font size, and a long sentence will cause the text in the scene unreadable, since some scene is kind of fast.

try not having sentence longer than this : "The buyer can write his answer as free text and upload a file." the same goes for text 2-5. *more sample on part 2*

UNLESS your intention was for the viewer just to take a glimpse of what is written, then sentences this long : "Structure your Buyer Instructions as free text, a multiple choice question or file upload." is fine.

Yes, there is add pictures extras.. ;)

Yes

Your choice between : 1. at the front cover - 2. displayed at right bottom corner for the whole video - 3. add 5 sec fade in to logo at ending scene -

Yes, but you must provide it.