For the engineer notebook, can it be an A3 paper notebook? Or preferable that it be A4?
Also, can it be blank pages on the inside not gridded or lined ?

The dimensions of the paper aren’t stated, so you could use a bound book of A3. However, given that conventionally, each page has only one date block, and thus covers no more than one day, you’d be crossing through a lot of white space. That’s pretty wasteful, and bound A3 books are pricey to start.

So A4 is more common.

Neither grids nor lines are required, but gridded paper is the conventional choice.

I guess you could use what you want, as long as you can keep it bound, organized, and professional. The judges need to understand it as much as you can.

Thanks guys