It all depends on the situation. If it weren't for certain policies that give minorities more opportunities to be chosen in the work force, it would most likely be dominated by white people as they are the majority and for quite some time minorities have been deprived of almost every social and economic opportunity. But even now, some companies are known for being biased towards potential employees who are white. It also has a lot to do with stereotypes and ignorance.
Depends, but in most cases yes. Civil suits would be a threat, but I feel like if the fear of being sued wasn't present, most opportunities would be given to whites. Whites make up the dominant culture, and it can be argued that they would like to keep it this way.
It would be almost impossible to find two people with similar credentials and the same personality, work ethic and how they work with other people. Depending on what type of person the candidate is and how he will interact with people and how well they will fit or fill out the group is what's important when credentials are similar.
I think a majority of companies would rather hire someone from the majority as racism against minorities still runs rampant, especially in the United States. I can picture companies hiring majorities over minorities at the risk of being accused of discrimination because many, but not all, minorities are still living in poverty compared to their white counterparts who work the same jobs and take care of the same household size of people and couldn't afford to sue companies for discriminating against them.