It sounds very weird and you know immediately it’s a foreigner speaking. When you are fluent the genders just come naturally, I don’t think I’ve ever seen a native making a mistake like that, maybe children.
I wouldn’t correct anyone unless they want to learn though, the noun itself is more important and it carries the meaning across.
This is for Brazilian Portuguese at least.
I don’t think so, I have premium and use firefox and so far no problems