She died of unknown causes. It is assumed that she died of natural causes. (Although it never revealed how did she die)
Spiderleg did not die yet in the series.
No, her death is not recorded.
So far she has not died, and it is possible she will not die in the series, but retire.
Leopardstar dies in Fading Echoes
Not so far as the end of the Power of Three.
So far she has not died in any of the series'. No one knows when or how she'll die or if she'll die by the time the Warriors series' is completely over. She will probably will retire before she dies because Jayfeather will need an apprentice soon.
The first series is just the Warriors series. It starts with Into the Wild.
Heavystep, a ThunderClan warrior in the Warriors series, dies twice in different books: once in a battle against ShadowClan in the original series and then again in a battle against the badgers in the later series.
Yes, Foxleap dies in the Warriors series. He dies in the battle against the Dark Forest.
'The Warriors' series of books are written by Erin Hunter.
In the Warriors series, the4th apprentice will be the first book of the 4th series.
Yes, she dies in The Forest of Secrets, which is the first book of the first series, bearing Graystripe's kits.