Training & Nutrition - Quads and clipless pedals

Right now I ride without clipless pedals. I dont know the exact terminology of the thigh-muscles group, so I'll refer to them as front thigh muscles and back-thigh muscles.

I feel like the front-thigh muscles are getting stronger than the back-thigh muscles. Is this normal?

If I get clipless pedals (and use them correctly) will it start improving my back-thigh muscles as well or do I need to do additional gym training (like when you lay on your front, have weights attatched to your feet, then you curl you feet back above your back-thighs, thus developing the back-thigh muscles) ?

If your pedal stroke is efficient (more of a shuffling motion than stomping/mashing), it tends to work your hamstrings (back of the quads) more. It's all in the pedal stroke.

Yes, clipless will work all the muscles in your legs. Well, all those that contribute to spinning the pedals, anyway. No gym work required. Just pay attention to your pedal stroke and try to get it to be a smooth spin: pull back at the bottom, unweight the leg coming up, push forward at the top and then not all that hard on the downstroke. Relax your ankles and try to feel the heel cup in your shoes. Pedal with your heels, not your toes. Relax your toes and try to pedal as though there were an air space under the ball of your foot. "Heels down and pedal round."

Especially, don't do knee curls like you describe in your post. Useless IMHO.

I think lifting helps actually. I've been doing leg presses , hamstring curls (the rear thigh muscles) and leg lifts to work the inner and outer thighs) for about 8 weeks now. I don't do power lifting, just lots of reps at lighter weights. I also don't do leg extensions, lots of stress on the knee.

I'm now spinning in higher gears than I was, and building up the lesser used muscles has helped me increase my cadence before I start getting the bouncy knee.

It's really bad bunga if your front and rear muscles get out of balance, that's a knee injury waiting to happen.

Your quadriceps are always going to be stronger than your hamstrings. That's how we're built.