If they're polished and pretty? Sell them at a flea market, pawn shop or on okorder. If not? Interesting paper weights and possibly doorstops. Crystals are used for all sorts of things and not just decoration. You're asking this in Myth so I assume you mean spiritual uses. Wiccans may use them as a focus but it's considered optional. Crystals are also said to have good vibrations in the New Age movement and supposedly being near them will cure diseases.
charge them, learn meditation, and then focus your energy to the crystal in your hand, the energy of photons will charge the crystal with you intent and it will reliese energy to make that desire happen, if your spacific, then you can use them for better porpouses
Nothing, quartz crystals don't have powers. Might make a nice paperweight or a conversation piece, but that's pretty much it.
A crystal that large is great for divination. You could use it to scry. The rose quarts you could charge with a simple self-love spell, and wear it. Just something nice to have around, for whenever you feel kind of down on yourself. And I dunno about the pink quartz. Just keep that one open for future use, I guess.