No, some brokers need a minimum deposit only 1$ to open an account. Some forex trading systems offer the facility of opening a demo account that allows you to check the efficiency and reliability of a particular trading platform. You don’t have to pay anything to open a demo account.

Nope, you do not need to invest all your money, because Forex trading is very risky and doesn't give any guarantee not to lose your capital.

It is not necessary to invest all your money on Forex because it is very risky to invest online. Invest the money that you can afford to lose, and expect nothing from your investment.