I have heard that spelling mistakes and grammatical mistakes are not counted in the ‘Listening Test’, is it right?
Absolutely not. Mistakes in spelling and grammar would cause you to lose marks. Though minor mistakes in grammar or spelling might be overlooked by the judges if those mistakes do not change the meaning of your answer and your answer is absolutely right and perfect. But don’t bank on making mistakes and expect getting marks. If you are prone to making mistakes you would make mistakes in other types of tests as well and won’t get any mercy for that. So be perfect with both your spelling and grammar.