I think simplefx allow you to open a demo account and a free platform for learning. Trading is a games of professional and it demand skill and high intelligent for you to really succeed in it. You should be advised that trading be it margins, arbitrage and buy and hold is very risky and you should not venture into it without proper skills and knowledge on how trading work
I am sure almost each and every Forex brokers are providing demo accounts. But learning about bitcoin or crypto currency trading will not be similar to Forex trading, but basics of trading are common for all types of trading. Only very few brokers for crypto currency providing metatrader based demo accounts.
Please read op post again. Op is looking for a brokers were he can trade btc/usd and using metatrade4 and also be able to trade demo. We should always read post before began to comment or contradicting comments.