A custom context which is developed within the IFS application may or may not have an impact with a service upgrade. That depends on the changes implemented on the upgrade being relevant with the customized entities on the custom context. Kindly note that, it is a technical limitation within the IFS Application that the custom configurations/contexts are not upgraded automatically with the service upgrade. 
 
However, after any upgrade a system user can log in to the ‘Page configurations’ window and check for any custom configurations that are affected. And the application is allowing you to “rebase the configurations” if there are any impacted areas. 
 
You can read more about this on IFS Application technical documentation  

 Tailoring guide> Configuration> Client side configurations -Aurena page designer> Rebase client configurations. 
 
https://docs.ifs.com/techdocs/22r2/040_tailoring/225_configuration/200_client_configurations/400_rebase_configurations/