Absolutely, you can claim whatever you want on your W-4 as it is just an estimate so that your employer knows how much tax to take from your paycheck. If you claim zero they will take the maximum amount of taxes from your check and at the beginning of the year when you file your taxes you will most likely receive a pretty large refund.
Pros of doing that are it acts kinda like a savings account you get the balance of every year, but the cons are if you need the money throughout the year you wont have access to it. I usually recommend people claim as close to accurate as possible. The goal should be when you file that you DEFINITELY don't want to owe (They hit you with fees), but you also don't want a huge return because that's money you could have been using all year long but you gave to the government as an interest free loan.
Yes. There is no requirement for your W-4 allowances to match the number of exemptions on your tax return.