The one used for tea is Hibiscus sabdariffa. The houseplant is Hibiscus sinensis. Rose of Sharon is Hibiscus syriacus. No, you can't use them interchangeably. This line of thinking is dangerous for it is like thinking that all Solanum can be used equally -- Solanum is the nightshade genus which includes food plants as well as ones that are toxic. Herbalists learn the botanical names for plants because certain plants are used in specific ways.

so there is no use for it at all? just decoration?. I know the Jap Beetles like them. duh

I did half the work for you. I gave you the botanical names. If you search for them on Plants for a Future, you will get their edible, medicinal, and utilitarian uses. Here is one: http://www.pfaf.org/user/Plant.aspx?LatinName=Hibiscus+rosa-sinensis