No. It isn't a bad/wrong practice, BUT, but only if you know what you are doing.
There is no problem using "using namespace std" in your source file when you make heavy use of the namespace and know for sure that nothing will collide.
However, you should also be able to write codes without using "using namespace std". If you work in an organisation and the supervisor of your specific project decides to ban the use of it, you'll have to be flexible switching to std::cout, std::string, etc.
No, its a standard practice.
Namespace is just a way of organising your code and giving you better understanding about the group which the code belongs to.
Its a good practice to use the std namespace especially when you are working on an official project.
It enhances code readability.
Ok for rookie but bad for pro's, as many older programs still in use are written without no namespace and use std all over the place. so knowing how to write good code without using no namespace is a good skill to develop also helps when understanding old code.
No. It's not a bad practice. But, it is necessary for the coder to actually know it's use. I know many people who only know it is used so that the program can compile, not knowing what it actually stands for or does. Make sure you don't become that kind.