I think you can access the servlet like that also.
/context-path/servlet/servletClass , if the servlet is inside the package , then /context-path/servlet/com.package.ServletClass (nothing but fully qualified class name).
so the first option is wrong.
the servlet is implements only doPost method but we are trying to access the servlet thro the URL which is nothing but doGet. so the server will return the error page.
Hope it helps