Marriage

Direct application to Hell

no its not fair

You mean at the same time or after divorce. If at the same time then you can give time to every person you are linked to.If after divorce then I think there is no harm, life must continue.

I think what you mean is a man marrying more than 1 woman, correct? If so, it depends on your beliefs/religion and how deep your understanding towards your beliefs and how devoted you are. Religion rules and fences were made beyond our rasionale thinking as a human because of limitation it naturaly brings.