Section § 2019

Explanation

An agent must follow the specific instructions and limits set by their principal and not go beyond what they are allowed to do.

An agent must not exceed the limits of his actual authority, as defined by the Title on Agency.

Section § 2020

Explanation
An agent needs to regularly update their principal about what they've been doing in their role.
An agent must use ordinary diligence to keep his principal informed of his acts in the course of the agency.

Section § 2021

Explanation

If someone is hired to collect a negotiable instrument, like a check, they must do so quickly and ensure all steps are taken to notify parties if it can't be paid. For bills of exchange, they must also try to get it accepted as soon as possible.

An agent employed to collect a negotiable instrument must collect it promptly, and take all measures necessary to charge the parties thereto, in case of its dishonor; and, if it is a bill of exchange, must present it for acceptance with reasonable diligence.

Section § 2022

Explanation
If someone is acting as a helper for another agent, that helper isn't directly responsible to the person who originally hired the main agent.
A mere agent of an agent is not responsible as such to the principal of the latter.