Oooh, even Biggest Loser, Yoga for Weight Loss doesn't require that a knee touches the floor during a lunge.... A lunge has one leg bent with knee perpendicular to the floor, with heel directly in line with the knee and the other straight back (or a reverse lunge goes the opposite).
Can you post a link to a video with the lunge you described? I'm just not picturing it in my mind.
One exercise is the lunge. Lunge forward with rt. foot until left knee touches the floor. Then lunge with lt. foot until right knee touches the floor. Repeat 5 - 10 times.
Start slow so you don't pull a muscle or injure yourself.
Cellulite is irregular pockets of fat, under the skin. Exercise and losing fat, overall, is the best treatment for cellulite.
Unfortunately, the creams/lotions don't usually do much good. There may be some that reduce the "appearance" of cellulite, but they won't get rid of it.