A photographed page looks like a photograph: grey, slightly uneven, a bit soft. A few adjustments make it read as a scan instead.
The difference between a photo and a scan is mostly tonal. A scanner produces white paper and black text. A camera produces grey paper and dark grey text, because it exposes for the whole scene rather than the page.
Pushing contrast separates those again. The paper goes white, the text goes black, and the uneven lighting across the page becomes much less obvious. Black and white then removes the colour cast that indoor lighting leaves behind.
There is a limit. Push contrast too far and thin strokes break up, faint pencil disappears and anything printed lightly is lost entirely. Check the smallest text on the page before you settle.
For most everyday purposes yes, if the page is square, sharp and legible. Some institutions require a genuine scanner.
Yes, if you are sending it as a document. Photos read as informal.
No.