The demo account is usually provided by the bot developer. They use fake charts, so you always make more profit while trading. They just want to make you believe their service (the bot) is good and win more than lose on long term. Their interest is only to sell their service and make their profit, doesn't matter if you will lose a lot of money with their bot on real account later...
I think it's not a good idea to trust a lot of money in a bot. It's just an AI, and it will lose all your money without any prudence.
Nope. Demo account on Forex Trading platform base their exchange amount on real time exchange rates. They provide this so that users can familiarize themselves on the platform and also it provides a good venue to practice trading style. The difference lies not on the exchange values but mostly on emotional and psychological effect of money on the user. Users are more relax using demo account so they can execute their trades properly. But on live accounts, they become emotional and sometimes panic sell.