3. Suppose you filed your taxes and received a small refund from the IRS. What would have been the impact on the refund amount if you had decreased the W-4 allowances for that tax year?

The effect would have been that the refund amount will have increased. The fewer W-4 allowances you take, the more is withheld from your paycheck for tax purposes. If you withhold more, you will owe less at the end of the year, so the amount owed will have stayed the same but the amount withheld would have increased.