Just type in Wikipedia and sperm in Google. Most of your questions will be answered.
Question 1 was a no. The tail develops later.
Question 2 seems to be around 130 days total, before they're fully ready (when they get ejected and die is up to the user I guess). Couldn't find a 'Use by' date.
Question 3 a sock, a tissue, I don't know? Look into it yourself.
Question 4 if you inject your semen into your blood, then, yes. Otherwise your body expels it.