Expense systems want a document, not a camera roll. One PDF with all the receipts in it is usually what gets approved without questions.
Whoever approves your claim is checking the amount, the date and the merchant. If those three are crisp, a slightly creased or curled receipt is not a problem. If the total is blurred, the claim comes back.
Receipts on till paper are the hardest thing to photograph, because they curl and reflect. Flattening one under a book for a minute, or holding it flat, makes far more difference than any adjustment afterwards.
Keep the order matching your claim. An approver working through a list of items should find receipt three on page three, and anything else adds friction to something you want approved quickly.
Usually yes. It makes checking straightforward. Several small receipts on one page is acceptable if all the totals are legible.
Raise the contrast before converting. Till receipts fade quickly, so photograph them early.
No.