Federal laws are the Supreme laws of the land. If there is a conflict between the two, Federal law prevails. State laws may be in addition to Federal laws, such as for some crimes a person may be...
Not quite... federal law is federal law and is in addition to state law, except where there is a state and federal law that are virtually identical, in which case the federal law may "supersede" the...
UPON RESEARCH I HAVE FOUND THIS ANSWER TO YOUR QUESTION FROM TWO SOURCES, THEY ARE AS FOLLOWS:
"A Federal agent generally has jurisdiction all over the country while a local officer has jurisdiction...