Is the full kit necessary or mainly the oil and balm?

Depends on the size of the beard and maybe the location. I have a big beard and live in NYC so I use all four items for the most part. Which exception of using the beard balm during the spring/summer because I feel it isn't needed as much. Had I have a smaller beard or starting out, I'd probably use just the wash & oil, and maybe balm.

Is the balm supposed to be hard as a rock?

Yes it seems normal to me that balms are hard ie. (Murray's Pomade.) If you will see the instructions you need to rub the balm in your palms until warm, then apply to beard. I must say that the Balm in this kit is my least favorite product and I only use it sparingly. Actually my son gave me his balm as he did not care for it. My son has a very thick beard compared to mine.

This beard shea butter products do it grow your beard????

No this is pretty much a nurturing kit to keep your beard clean, moisturized, and looking good. It does keep your beard healthy however it isn’t to grow your beard like other supplements