Bed Lever Will Sit-ups/crunches Have The Same Effect If I Slide My Feet Under My Bed?

Will sit-ups/crunches have the same effect if I slide my feet under my bed? - bed lever

I am 14 years old and abdominal muscles, I walk 30 minutes per day at home and 30 minutes after school. I do every day kg 100 repetitions with weights of 5 and I noticed a fat roll? Now my brother is very fond of me and said you do not need a gym only occasionally a ton of sit-ups a day, but I'm sitting in despair, and I wondered if I slip my feet under my bed and use it as a base, which I can do squats in this manner because it is the only way I can have the same effect?

If not, what can be done to get the muscles of the stomach ?????