Find the theoretical probability of:

1. Drawing a red ace or a heart from a regular deck of cards.
2. When guessing the birthdays of two friends, getting exactly one right, if you know the first friend was born in a leap year and the second friend wasn't. Assume birthdays are evenly distributed through the year.
3. Being dealt at least 4 hearts in a hand of 5 cards dealt from a regular deck.
4. When selecting 3 cards from a regular deck without replacement, having the 3rd card be the second spade drawn.