Here are the required times for Silver rankings on the challenges. For general tips and the times required for Gold, see the solution and/or comments for Gold x 50. Short version is watch the playbacks of the leaders in the leaderboard to see how it’s done. Often I would watch the leaderboard video(s), but then also open a YouTube video so I could pause my game and watch the next segment as I move along. Pausing with the “back” button on your controller instead of “start” will pause the timer. Also the default button is RB for the MM1 pause glitch to work against bosses (you’ll see this in a lot of the MM1 boss fight playbacks).
MM1 Remix 1: 2:30
MM2 Remix 1: 3:00
Yellow Devil: 2:20
Mecha Dragon: 0:45
Craig’s Challenge: 4:00
MM1 Remix 2: 4:40
MM2 Remix 2: 5:00
MM1 Robot Rush: 2:40
Wily Machine 1: 1:20
MM1 Megamix: 5:00
MM2 Robot Rush: 3:30
MM2 Megamix: 5:00
Wily Machine 2: 1:00
MM1-2 Mashup: 6:30
MM3 Remix 1: 3:30
MM4 Remix 1: 3:10
Yellow Devil MK-II: 1:15
Square Machine: 1:30
MM3 Remix 2: 4:00
MM4 Remix 2: 5:30
MM3 Robot Rush: 3:45
Wily Machine 3: 1:10
Cossack Catcher: 0:50
MM3 Megamix: 5:00
MM1-3 Mashup: 6:45
MM4 Robot Rush: 5:15
MM4 Megamix: 6:30
MM1-4 Mashup: 7:40
Wily Machine 4: 1:30
MM5 Remix 1: 3:45
MM6 Remix 1: 3:00
Big Pets: 1:00
Mechazaurus: 0:55
MM5 Remix 2: 7:00
MM6 Remix 2: 6:10
MM5 Robot Rush: 4:50
MM5 Megamix: 6:30
Wily Machine 5: 4:15
MM1-5 Mashup: 7:45
MM6 Robot Rush: 4:45
MM6 Megamix: 5:30
Wily Machine 6: 1:15
MM1-6 Mashup: 10:00
All Appearing Blocks: 2:35
Dr. Wily Forever: 10:25
All Robot Rush: 26:00
MM1 Robot Rush (No Items): 4:50
MM2 Robot Rush (No Items): 8:30
MM3 Robot Rush (No Items): 10:15
MM4 Robot Rush (No Items): 10:50
MM5 Robot Rush (No Items): 7:45
MM6 Robot Rush (No Items): 9:00
All Appearing Blocks (No Items): 4:40
All Robot Rush (No Items): 50:00