Every problem here borrows. The generator keeps only the two-digit pairs where the top ones digit is smaller than the bottom one, so the ones column cannot be subtracted without regrouping from the tens - the step students skip when a page lets them.
Answers never go below zero; the generator orders each pair so the larger number is on top. Once borrowing is reliable, move Regrouping to Both so the page stops telegraphing that every problem needs it.
When the digit you are subtracting is larger than the one above it, a ten is broken out of the next column so the subtraction can be done. It is the same thing as borrowing.
Carrying adds a digit to the next column, which is a single extra step. Borrowing changes two columns at once - one goes down, one goes up by ten - and the changed digits have to be tracked. Practising it in isolation, as this page does, is usually what fixes it.
No. Each problem is ordered so the answer is zero or greater.
Set Regrouping to Both and the page will mix the two, so a student has to work out which each problem needs.