Is corckscrew leaf a cumpound leaf?

it is compound pinnate

Single leaf

if you are talking about the flag no it is not but if you are talking about the leaf then yes it is a leaf and it is common

There is no why. There is only do. Sheaf is pluralized sheaves, thief becomes thieves, and the verb grief takes the form grieves. You'll be interested in investigating the root of the word "Sheriff,"...

No, it's a simple leaf.