This sounds like you're using an after() method that disables the functionality of the hybrid controller. You should assign the theme template in the before() method to $this->template. You should not touch the after() method.
Your standard actions then assigns template partials to $this->template
Your REST actions don't, they return a response containing your REST data, or an array that after() will convert to JSON.
i am using after method, without after, theme will not work in template controller, now i have an theme controller which is set by theme, and all backend controllers are extended from it,
If you use a theme in the template controller, the same is true.
Don't manually try do some all sorts of stuff, since you disable the processing in the parent controller. Instead, use the before() to assign you theme page template to $this->template, and use that in your controller actions.
Because you have created your own after method, the Fuel base controllers no longer work.