In which scenario do the different court systems in the U.S. interact properly?

• When a landlord tries to file a complaint against a tenant in Oregon after he loses in a Washington state court, the Oregon state court allows the second case to proceed.
• A Montana state court refuses to hear a civil lawsuit with a false imprisonment claim, because the complaint references both Montana law and federal law.
• An Indiana court hears a case related to an auto accident that happened in the state between residents of Ohio and Illinois. When trying the case, the Indiana state court judge considers the laws of Indiana, since that's where the accident occurred.
• When a waitress in Virginia sues her employer over unsafe working conditions, the state court judge applies the laws of Virginia, even though federal regulations governing workplace safety are more stringent than those of the state.