What happens to custom_variables and its values post upgrading the AMP to 8.2.8 version
Post 8.2.8 AMP versions, there will no longer be a custom_variable functions in the template or the Manage page.
This has been changed to dynamic variables.
Before the custom _variables were limited to 13 and now there is no such limitations.
So if customer had IAPs with custom_variable set in older version of the AMP, and when they upgrade the AMP to 8.2.8 or post 8.2.8 version, the custom_variable and its value does not get wiped out but will be seen under the dynamic variable as seen below:
The custom_variable if defined in the template will remain as custom_variable when upgraded to 8.2.8.
Newer variables that you define post 8.2.8 could be intuitively named as they will be considered dynamic variables.
This has been tested and replicated in lab.