i agree with @nicolas hung so please read his answer first, i want to add on it.
You can sometimes break these rules so when to break the rules depends on some factors, consider those:
1. Are your users willing to learn?
to answer this you need to consider aspects such as how experts are your users? how much do they value/need your product? and whatever is relevant to your users that would drive their willingness to learn - you should know your users better.
2. Do you have a good reason?
Is context menu not important? do you have something more valuable? have you invented a better context menu?
3. How often do they use your app? How often do they right-click?
If they are infrequent users, even if they have learned what your new right-click does, they are likely to forget and fall to the mistake, here are your probable scenarios
User Frequency | Right Click Frequency | Break the rules? | Why?
High High Yes User got used to it
High Low Fine User will take time but is likely to get used to it
Low High No This is where the user smashes his head to the desk and wonders how many times does he need to remind himself
Low Low No Just don't do it
This does not necessarily capture all of the factors, but it can guide the approach before deciding to break the rules.