What is the point of bitcoin if the value is directly tied to another currency?

well this stuff isn’t Bitcoin, that’s a separate system entirely, and the point isn’t for these stablecoins to rise over time. the hope with them is that by using the dollars relative stability they can be used to conduct financial transactions that have a much more stable value than using something like Bitcoin

for example the prediction-betting site Polymarket uses a stablecoin called USDC for its transactions, instaid of some other cryptocurrency

its decentralized in a sense that it’s extremely difficult to reverse transacitons and that you can keep money in a wallet without people being able to take it from you, but the value of it is set by a single company so it’s isn’t really decentralized

idk how to answer your second question