Short answers, pulled from the story.
India contributes 75 percent of global spice production. Production data from 2010 and 2011 show India generating over 1.4 million metric tonnes annually, far ahead of the next largest producers Bangladesh and Turkey.
The most common spices in medieval Europe were black pepper, cinnamon, cassia, cumin, nutmeg, ginger, and cloves. All were imported from plantations in Asia and Africa, making them extremely expensive; around 1,000 tons of pepper and 1,000 tons of other spices entered Western Europe each year during the Late Middle Ages.
Vasco da Gama sailed to India in 1499 primarily to find a sea route to the pepper market that would bypass Venice's monopoly on the spice trade with the Middle East. Finding pepper at much lower cost in India than Venice charged justified the entire voyage commercially.
No. This claim is false. Spices were expensive commodities in medieval Europe, and contemporary cookbooks show they were added late in cooking, where they could have no preservative effect. The writer Cristoforo di Messisbugo even suggested in the 16th century that pepper might accelerate spoilage rather than prevent it.
A whole dried spice has a shelf life of roughly two years, while a ground spice retains meaningful flavour for only about six months. Grinding greatly increases surface area, which accelerates oxidation and evaporation of the volatile oils that carry the spice's flavour.
The discovery of the New World introduced allspice, chili peppers, vanilla, and chocolate to the global spice trade. These additions kept the spice trade profitable well into the 19th century.