Short answers, pulled from the story.
The Anglo-Polish alliance was formalised by the Anglo-Polish Agreement on the 31st of March 1939, with additional addenda signed in 1940 and 1944. A broader mutual assistance agreement was signed on the 25th of August 1939, two days after the Molotov-Ribbentrop Pact.
The secret protocol specified that Britain's firm obligation to assist Poland applied only in the case of an attack by Germany. If Poland was attacked by any other country, the parties were required only to consult together on measures to be taken in common.
No. When Soviet forces invaded Poland on the 17th of September 1939, Polish Ambassador Edward Bernard Raczyński argued that the alliance's clause covering any European power should apply. Foreign Secretary Halifax responded that Britain's obligation, as defined in the secret protocol, was restricted to Germany.
Britain agreed on the 2nd of August 1939 to grant Poland a military loan of £8 million. Poland had requested £60 million, and Turkey received a larger sum from Britain at the same time.
The Moscow talks in August 1939 failed for several reasons. The British negotiating team lacked authority and moved slowly; William Strang, an assistant under-secretary, led the British delegation. Poland refused to allow Soviet troops to cross its border, fearing they would never leave. The Soviet Union then shifted strategy and signed the Molotov-Ribbentrop Pact with Nazi Germany instead.
The historian Paweł Wieczorkiewicz wrote that Polish leaders were unaware that Britain and France were not ready for war and were buying time at any price. The publicist Stanisław Mackiewicz called accepting London's guarantees one of the most tragic dates in the history of Poland, a mental aberration and madness, writing in the late 1940s.