4. (b) That's wrong. It would be unfair to hold an employer liable for wrongful acts of their employees if those acts had nothing to do with their employment. So the rule is that if employees engage in some activity unrelated to their work (sometimes referred to as 'a frolic of their own'), then the employer is not vicariously liable for harm that ensues.
Nevertheless, an employee may be acting within the scope of their employment even if their wrongful actions are deliberate and against the employer's express instructions or wishes, and even if the conduct involves a criminal offence.
The same rules apply to principals and agents, and partners.