Play a message to the called number, when answer

You can play a message to the called party using the Custom destination "Play to the called party when answer"

The objective is to create a feature code, like *1021[NUM] that will execute the about custom destination and then connect the call to the [NUM] entered

You need to create a custom destination to forward the call to the number of your choice, passed as parameter for the feature code:

You can use also a Forward To Custom destination, allowing more parameters

Here the final feature code: