I'm having trouble with the final magic plant too (but it's not the rosacae fern. I'm fine on that one). I got rid of all my citrus ball cacti a while ago, not realziing they'd be needed, and I was hoping there was a way to cross polinate other citrus plants to try and get the citrus ball cactus back. I have tried to purchase seeds from the shop, but so far, no luck. Will the seeds in the shop replenish themselves so that I can have another chance at getting the citrus ball cactus back, or is it that once seeds are purchased, that's it? And, what's a Tier 4 plant?