Employment Law Questions? Ask an Employment Lawyer.
Ok. The fact that you are young isn't helpful. That's not a protected category. An employer is actually allowed to discriminate against youth and in favor of the older employee. That's actually in federal statute.
It's also not illegal for a manager to promote their favorites. Personal bias, not based on race, religion, gender or disability, is not actually illegal. So, you have to be prepared to make the argument that the only reason you are not being promoted is your minority status.
If you feel that is the case, your option is to either make that very direct complaint to HR (where you expressly state that you believe you are being discriminated against based on your minority status) or you have to file a complaint externally with the Equal Employment Opportunity Commission. This is a protected activity, meaning that the employer cannot retaliate against you for making it.
Yes, because there actually isn't a law against unfair or uncivil treatment. The law only prohibits forms of discrimination made illegal by statute.
The compensation piece is only useful to the extent that it can demonstrate discrimination based on race, religion, gender, etc. There is not any law concerning the difference in pay between a supervisor and direct report, so it's not automatically problematic for the pay issue itself. Again, it is only useful as a fact which can suggest discriminatory decision making.