Unlike commodity futures, financial futures are generally just a concept of value. There are many kinds of USD futures, including EUR USD, JPY USD and GBP USD. You don't care what currency you pay for the contract deposit. There are also interest rate futures, which is even more unreasonable if you buy interest rates.

Not Eurodollars, but Eurodollars, partly for hedging. For example, China export enterprises are afraid of the exchange rate risk brought by RMB appreciation, so they can avoid the risk by buying RMB-USD futures.