Broadly speaking, assets denominated in foreign exchange, assets that can be cashed abroad, and even domestic currency used to prepare international payments can also be counted as foreign exchange.

There are many forms of foreign exchange reserves: foreign currency, foreign short-term deposits, gold, foreign government bonds, foreign corporate bonds, foreign stocks or other securities, etc.

There may be a large number of holdings in the form of money, but it is not common. After all, the foreign exchange risk is still relatively large. Who doesn't want to find some fixed-income securities to balance risks? The main form may be national debt.

As for the second question, that's impossible. The exchange rate is changing at any time, which is risky. It may become more or less.