I am dead sure that the earth revolves around the sun.
Bob was dead.
Example sentence - The bug was dead as a doornail after he stepped on it.
Working at that place is a dead end job.
They wanted to catch him dead or alive as he was a dangerous criminal.
Example sentence - The dead battery in the truck had to be replaced.
Sure
a man found a dead person floating in a sea while fishing.
By making sure the sentence does not make sense.
Sure, I can use "so" at the beginning of a sentence.
Dead to the world means sleeping soundly. One example of a sentence with the idiom dead to the word is: After working a double shift, Sarah fell asleep and was dead to the world.
My college dorm is a dead zone for my cell phone reception.
Sure, this a complete sentence.