I have not yet begun to fight

Q1: “Has your ship struck her colors? = Has your ship hit the flag of my ship?

Q2: with shot = firing guns? why is 'shot' not in plural form?

Q 3: “I have not yet begun to fight = Did Jones mean the British captain was self-defeating?

Could anyone possible explain why this quote becomes famous among American midshipmen?

Thanks!

On August 14, 1779, Jones sailed on the voyage that made him famous. Off the North Sea Yorkshire coast, he encountered a forty-four-ship Baltic convoy laden with naval stores for England, under escort by a fast, maneuverable, fifty-gun British frigate, HMS Serapis, commanded by a veteran Royal Navy captain. Jones attacked. The battle, beginning at 6:30 p.m., continued for four hours under a harvest moon. The two ships, locked together yardarm to yardarm by American grappling hooks, pounded each other with shot. At one point amid the carnage, the British captain called across his deck to Jones, “Has your ship struck her colors?” He was referring to the signal of surrender. Someone heard—or perhaps a writer sitting at his desk later imagined—Jones call back, “I have not yet begun to fight.”The battle continued until, with Bonhomme Richard sinking and Serapis on fire, the British captain suddenly struck. Jones transferred his wounded and the rest of his crew to his captured prize, put out the fire, and returned to France.

Naval Academy chapel. Since then, every midshipman has been taught Jones’s words, whether they were exactly his words or not: “I have not yet begun to fight.”