Are any descriptions of Rudra's aspect ? If yes, where we can find them?

I am referring to this book Исцеляющие мантры в Аюрведе (Russian Edition) (Healing Mantras in Ayurveda). There is a Mantra for gaining children. It is said, that this Mantra is written in Atharvaveda. I sounds like this: Yena Vahad Babhivitha Nashaymasi Tat Tvam Idam Tadaniyatra Tvadaha Dure Nida...

Like I know that the names of Manu changes. So does the name of Indra and the Saptarishis. What other things/names change ? And are all events of each kalpa identical to each other ?

Goddess Durga's fifth form is called Skandmata, and she holds Lord Kartikeya. However, despite the many stories of Goddess and her love for Lord Ganesh, there is no avatar of her holding Lord Ganesh. Is there a reason for this?

Basically, what I am asking is whether all humans have lived as other beings or not. I heard that everyone attains human birth after progressing through 8.4 lakh stages of being born as other beings (animals, plants, etc.). I may be incorrect.