First, the meaning is different.
Knock off means robbery.
2.knock over means: knock down; rob
Second, the usage is different.
1.knock off Usage: It is an abstract noun, but it can be counted. It can be modified by indefinite articles, and it can also be used to express plural concepts in plural forms.
Example:
The police sealed off the area to prevent robbery.
The police sealed off the area to prevent robbery.
2. Overturn usage: It can be used as a transitive verb or an intransitive verb. When used as a transitive verb, it can be a compound object with a noun or pronoun object or an adjective as a complement. Can be used for passive structures.
Example:
The gang robbed a jewelry store.
The gang robbed a jewelry store.
Third, the emphasis is different.
1.knock off key point: nothing has happened yet, and it is in the prevention stage.
Overturn point: something happened.