Answer:
I start in little but I end in full, you'll find me in half and complete.
Ambitious people will climb the social version of this contraption.
What does someone else have to take before you can get?
a king,and Queen walked outside it was dark outside when they walked back in another person was with them,Who?
No sooner spoken than broken. What is it?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.