Chomsky says that children have an innate language Acquisition device which helps them acquire language. Is it available even to adults who try to learn a second language?

The hardware that allows easy language acquisition only lasts until we're about five years of age. If no language has been learned by that time, it is very difficult to learn any at all. There have been studies on so called "wild children" who were not exposed to human language until their teens who were unable to learn any language at all.