Answer:
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.
hide me from your parents if you have done bad academically this year.
I have 24 keys but cannot open any locks. Sometimes loud sometimes soft
You may enter, but you may not come in. I have space, but no room, I have keys, but open no lock. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.