Missing levels: Spooktacular Bay, Challenge: Halloween Invasion, The Striking Tree, Challenge: Tavern Incursion, Lover's Paradise, Lifestream Hollow, Tropics of Etheria, Crystal Cave, Challenge: Eternia Gauntlet, Frostdale Wonderland

And can the new levels be added? Such as The Striking Tree and Spooktacular Bay

Can Ruthless difficulty be added to level runs? Right now campaign runs have it, but levels do not.

Sure!