The symbol of SkyClan was revealed in one of the super editions, Battles of the Clans. It's in the same style as the other Clan symbols, with its distinctive mark being a cloud-shaped tree. A picture of it can likely be found somewhere online (scans of the book, fanart, etc.) or within Battles of the Clans itself.
We will find out in Skyclan's Destiny.
In the books "Firestar's Quest" and "SkyClan's Destiny" in the beginning of the books.
You can find it on google
You need to look up Erin Hunter. I am not familiar with the Warrior series and Skyclan so you will find the information you need at the link below.
Echosong joined SkyClan because she kept on having dreams about SkyClan's ancestors. Although Echosong is the medicine cat of SkyClan she has no SkyClan ancestry.
The symbol for radiation is the "radiation trefoil", and you can find it by that name. I've added a link below.
There is a picture called Martyr's Mirror that contains Felicitas of Rome. Her symbol is a woman holding a sword with seven male heads on it.
I doubt it.
There is no current answer, but one clan has completely perished which is skyclan. Find out the ways it is reunited by reading skyclan's destininy. By the way the proper grammar is when are the warriors going to die
Yes, and it is called Skyclan's Destiny.
Yes. Echosong is medicine cat of Skyclan.
its Starclan and maybe.