I just beat every Solo Event on Hard yesterday, and beat every reward condition.
If people want help, feel free to ask me. I found some good strategies for some Events.
Since a lot of people have trouble with Robotic Rampage, here's a great strategy - at first, spam side B to rack up damage. Then, when the platform lands on the small beach island (it's always the first stop in this Event), knock the Giant Metal R.O.B into the water (or sometimes he just wanders in). As soon as he's in that water, D-AIR LIKE YOU JUST CAN'T STOP. You may recall from Brawl that Metal characters sink really far down into water before they swim back up (it was actually used for a secret in the Subspace Emissary, where you'd swim under a wall using it). While characters are in water, they can't attack. So basically, you keep D-airing the Giant Metal R.O.B while he's trying to swim back up, and every time you it him, he will sink REALLY far down. This keeps him in a lock, and if you keep doing this until the travelling platforms are lifting off again, he just get's K.O'd by the bottom blast zone that moved up into him. This strategy makes this Event pretty easy, even on Hard, and you will meet the reward condition too.
Also, I actually didn't have any trouble with The True Final Battle. It took me three tries. While this is easier for me to say since I main her, if you are half decent with Rosalina, use her for this Event, as she is particularly good for it. CPUs completely ignore Luma the majority of the time, so just send him out at them. I recommend going for Mega Man first, as he can screw up this strategy (since he will accidentally interrupt Luma by trying to shoot Rosalina). Once you get rid of him, it's really plain sailing. Sonic will just predictably spin about, and Luma Shot interrupts that even when it is uncharged. Mario is no problem as long as you take him on with a linked Luma (he can and will try to reflect Luma Shot if you use it too much), and you should really try to make sure at least Sonic and Mega Man are gone by the time he shows up. And with Pac-Man, just keep below the platforms, so he can't hit you with the hydrant. He will often use Neutral B and Side B, but it's really easy to read these, especially if Sonic and Mega Man are already gone. Also, in general, know that off stage gimping (especially on Mario) is good for killing, as well as pushing people off the top of the stage with Rosie's Up-Air. And of course, if you really wanted extra insurance, you can use equipment that gives Rosalina some all-around buffs.