Weekend Demo MT5 Account
Demo accounts and functionality of demo accounts depend on the broker.
Because all demo accounts and all the symbols to trade (and specification of the symbols proposed by broker to trade) are related to the broker only.
So, Metatrader has nothing to do with any demo or real/live account.
Besides, forex market is closed for weekend ...
There are some brokers that proposed cryptos for trading during the weekend on their account (but as I said - it is related to the brokers only).
As far as I know and have experienced, synthetics (like boom & crash) and cryptocurrencies (like bitcoin, etc.) also trade on weekends, on many brokers (but not all).
Use the tester.