Hi Mary Ogbadoyi
Welcome to the Scoolinary community, and thank you for your question.
A sponge cake might be a bit too delicate to support the weight of fondant. As a suggestion, you could use the Quatre-quarts Cake recipe that is included in the course.
You can definitely use white brigadeiro and lemon fudge as fillings, but remember that you should first create a containment ring with ganache to prevent the filling from seeping out of the edges. Additionally, before covering the cake with fondant, make sure to apply a crumb coat of ganache, followed by a second layer of ganache to smooth the surface of the cake. After completing this process, you can then cover the cake with fondant.
This cake can last 2 to 3 days at room temperature (21°C to 23°C). We do not recommend refrigerating it, as the fondant layer could be damaged by the humidity in the refrigerator.
We hope this information is helpful.
Best regards.