Just because something exists doesn't mean everyone is entitled to get it, like the incredibly low drop rate on Dark Boss set items. Genesis weapons aren't like the new viable endgame weapon, they're a bonus like the dark boss set. There's nothing wrong with that.
Also, we only know the restrictions for the first one or two fights (just Von Leon, and I think someone managed Arkarium), and they're not the same across all the bosses. No one has done the other bosses, so we don't know how those are restricted, the only thing we know is that there are 3 different debuffs: Up to -90% Final Damage + Equip Restrictions, -20% Final Damage, and only being able to use a certain type of potion. It's a bit too early to complain about how impossible it might be when we don't even know yet.
Bonus stats can alter an item's level requirement, but when it comes to transfer hammer, it uses the item's actual level requirement, not the level after the level requirement reduction bonus stat. You would be able to transfer it to an Absolabs cape no problem.
2,100 medals is just the cost to reach the rank of Hero II, it shouldn't have any effect on any other medals you spend on any other items. Speak with Neinheart to hear the explanation on Alliance ranks.
The issue isn't how much you spend on other items, it's how the mission states "on one character", which seems to imply you have to do all your rank ups on the same character.
Items from Surprise Style Boxes (the non Premium red ones), are usually temporary (with the possibility of some permanent items from a small pool, which hasn't been updated in like forever) and tradeable, so that's probably the source of your temporary item. It's possible, but since most people just buy premium boxes, I wouldn't exactly consider it normal.
It's not currently immediately obvious which cash items are temporary or not (unless you happen to have a good memory and sense of which items were released in all the permanent boxes), and I think someone complained a while back about how they don't even show expiration dates, but I'm unsure if that issue has been resolved.