Christianity believes that Jesus Christ will return to the earth as King and rule for 1,000 years. All other religions will not be tolerated. Lucifer will make one last attempt to usurp Christ after the 1,000 year reign and then he will be cast away for good. There will then be a new heaven and a new earth. All those who do not accept Christ will be destroyed with Lucifer.

That's the hard simple facts of Christianity. Unforgiven sinners (those who reject Christ) will eventually be destroyed. All other sinners will live in peace (those who have been forgiven because they willingly accepted God's gift - Jesus Christ dying in their place.)

As for now, the example of how to live until Christ's return is laid out in the Christian Bible. It's not all black and white. They are allowed freewill. Their salvation will not be judged, but their faith will be judged and their future responsibilities will be on the line.

No matter how some Christians may sugar coat it, this is Christianity in a nutshell. To be a Christian, one must be saved. Their works are not towards the salvation they already have, but towards their membership in the times to come.

So, yes, just as a Christian can be a loyal member a democratic, rather than the truly Christian theocratic rule, a muslim can be a loyal member of a non-muslim government.