The title says it all.
If you put the LEDs in series, no, you only need one resistor per chain.
without the resistor, you will burn out the LED. The LED will make ONE blink... and thats the last light it will ever put out. There are lots of instructables for using LED's. Just do a search on that subject.
No, or yes, or maybe. What have you got, what do you want to do? L
Yes. Yes you do. Here's a nice website to find out which ones:http://led.linear1.org/led.wiz