In other words, the boss can't fire you without giving you ample warning. Yes, so long as they are not discriminatory or do not significantly burden an individual employee. Rules that set different standards for men and women without any legitimate business reason for doing so may be discriminatory. If an employer can show that a dress code is job-related, it will likely be left intact. And if the rules are found to be reasonable, an employer generally can fire an employee who refuses to follow them.
Most states prohibit employers from withholding a person's salary for disciplinary reasons.
In addition, employers must pay workers the minimum wage set by Federal law. If a dock in pay dropped a person's wages below that level, it would be illegal. Generally, yes, depending on state and local law. Employers are free to restrict smoking in the officeplace. They can ban it outright or restrict it to designated areas.