If the police stopped you for speeding then arrested you for something else, they would usually list the speeding charge on the criminal complaint. You should speak with a criminal defense attorney about the specifics of your case. Good luck.
Not always. You have not mentioned what the other charges are. Speeding can be used as a basis for a vehicle stop which can lead to additional charges, both traffic and non-traffic (criminal) charges. You should speak to an experienced criminal defense attorney about the stop and charges that have been filed.