Going from demo to live

Experienced trader, but new to futures trading. Have been using the demo for some time and opened the account and plan to use the demo for some time before going live. What are some things to watch out for when going live? Is the market data used in demo same as in Live?
I read somewhere that in demo a limit order will be triggered when the price hits that level, but in Live, you have to wait until your place in the queue?
I am planning to day trade, does tradovate liquidate in the middle of the day if you exceed the margin or only at 4:45?
Not quite clear about the initial margin and maintenance margin. Does that come into play only if you hold it after market closes?