Sperm can live for 4-5 days in warm, moist conditions such as the vagina. However, once dried sperm will die within a matter of minutes. If you had wiped the semen from your hand onto your vagina immediately after its ejaculation you would indeed be at risk for an unintended pregnancy.
It depends. I honestly dount it though, pregnancy can really only happen around the time your ovulating. Also sperm can only be in oxygen for a few seconds before it dies