You posted on my trade shop, my shiny seel is already pending on a trade. You can ask for something else currently on there, or if you're able to clone. I'm about to make a big update to the shop so you can check back later.
Very sorry to hear about your scam case, it's always a terrible thing to go through.
To check if the Arceus is hacked, legitimate Arceus can have Event OT's, like MICHINA, TRU, えいがかん, and a few others. But if its anything not an event, it needs to come from the Entree Forest and be Lvl 100.
To check if the Darkrai is hacked, legitimate Darkrai can have an Event OT like the one above. If it has a Trainer OT, then it should also be higher than or at level 50 and should not have a Fateful Encounter.
Anyways, hope you can get your case resolved, and hope I could help.