It just be two because it would just look weird as one(headstart) but you could make it one with a hyphen(head-start) that would also look good. It depends on how you are using it. If you use it in a sentence, such as, "I got a head start in the race today," it is written as two words. If you are using it as a company or program name it depends on how they choose to write it.
Head start is two words.
La cabeza
Off the top of my head, I believe that I can.
It should start with (mis) :)
No, you should not. You should only capitalize a word when it is at the start of a sentence or when it is a proper noun.
no
The word "hairbrush" is typically written as one word, not two.
Yes. Every sentence should start with a capitalized word.
Written as one word (hogshead) it is a very large cask (wooden barrel)
Generally, it's one word.
However. On the other hand.
No, why should it be? Well if it's at the start of a sentence, but really, how many sentences start with the word example?
Underdeveloped should be written as one word, not two words or hyphenated. I hope this answered your question. :)