You can do Full Medal runs in one go by abusing the glitch that deactivates the in-game timer. However, it does activate if you go through the portal to the obsidian skull, so you'd have to do that as the last thing in a level to have enough time left for the full medal.

Not sure if this is applicable to each and every stage, but it does make Full Medal Runs more viable, since you wouldn't have to do each level twice.

Timer was activated once again after walking through the doorway at the start, which means that the loading screen is what makes the timer come back to life.

The pause menu was disabled by the Timer Freeze glitch Nothing unusual happened after winning the race

I tried reload checkpoint for a little bit and don't think it can freeze the timer.

Estimated what a playthru would look like using Timer Freeze on every level.

1-1: Breaking In 0.000 1-2: A High Detour 0.000 1-3: Twisty Bridge 0.000 1-4: Perilous Aqueduct 0.000 1-5: Race on the Topside 0.000 1-6: Prickly 1.02.916

2-1: Trap Hall 0.000 2-2: Goopy Swamp 0.000 2-3: Drippy Caves 10.488 2-4: Ancient Sewers 0.000 2-5: Stream Racing 0.000 2-6: Kicky 1.20.024

3-1: Pushy Hallway 0.000 3-2: Mountaintop 0.000 3-3: Cold Cave 0.000 3-4: Slidey Spikey Cave 0.000 3-5: Mountain Jog 0.000 3-6: Wintry 2.08.565

4-1: Steep Descent 0.000 4-2: Magma Bathtub 0.000 4-3: Temple of Fire 0.000 4-4: The Tar Swamp 0.000 4-5: Hot Feet 0.000 4-6: Scorchy 2.50.393

5-1: Spiky Hallway 0.000 5-2: Mirage Cave 0.000 5-3: Chamber of Spooks 0.000 5-4: Dark Dark Place 17.153 5-5: Running With Fear 0.000 5-6: Hexy 2.04.315

6-1: Gateway to the Core 0.000 6-2: Golden Depths 0.000 6-3: Treasure Vault 0.000 6-4: The Foundry 0.000 6-5: At the Finish Line 0.000 6-6: Beelzebub 3.54.026

IGT total is 13:45:880

Using the level timer to measure would trivialize almost all of the gameplay, don't think that's a good idea. Also, in speedrun mode the timer continues no matter what happens with the level timer. So my point was to make Full Medal runs more viable (bc without the glitch you'd have to do each level twice to get a full medal).