The king and duke were merely con-men pretending to be royalty. They met in Huck's raft because they were running away from the authorities who discovered their con.
They were initially strangers but upon knowing that each was a conman. Both hatched a plan to con numerous people by staging a play like Romeo and Juliet.
Blank verse for is c) a type of verse with no rhyme scheme but a meter in iambic pentameter. Shakespeare often wrote in blank verse, many of his plays (if not all) were written in this type of verse.
