I believe there is an option to connect the games for Memory Link. The main site says it's done via Wirless or WiFi and both games need you to use Game Sync(Not sure if the Game Sync is referring to Wireless and WiFi or just WiFi). As for the flashbacks, I believe once you do activate Memory Link you just talk to certain characters and the flashback will trigger.
Originally Posted by KantoLegends
As for Challenge Mode, Gym Leaders all get an additional Pokemon(In Burgh's case he replaces his Swadloon and gets another Pokemon), the Elite Four as well get an additional Pokemon(Not sure if there is any replacements though). Along with the extra Pokemon for them, they gain levels for their Pokemon(The levels go up as you advance I believe, I think it goes up by 1 for every two Gym Leaders(So +1 to 4 levels) the Elite Four and Iris have +4 too I believe), trainers also gain levels I believe, apparently after defeating Iris everything is +5 levels. There's also move changes and items being given in certain cases, not sure about the Trainers but any unique spirit I think for the most part gets an item and a move change here and there. The artificial intelligent is supposedly higher too for everyone I believe. So it's certainly more challenging, kind of hard to say how harder as the games are adjustable to start off with, but you should end up with more work on your hands doing Challenge Mode.
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