That depends on your level of comfort with that one person. If there's a group of people whom you love and are close and comfortable with, would you open up to them and communicate without restricting yourself?
In my opinion that alone doesn't make u an introvert.
I'm not close to anyone actually
I don't hesitate to talk or fear but I'm bad at maintaing group of friends
Then I don't think you are conclusively an introvert. Being an extrovert doesn't mean you hang out in groups and have a huge social circle.
I always feel low when I'm in groups but just pretend that I'm happy
Like I said, there isn't enough evidence to label you an introvert. You just do not like being surrounded by a lot of people, which is totally alright. Perhaps you're an ambivert!
when I'm the centre of attraction I like to be with lot of people when not I will be just sad but individually to everyone in that group Im close but I don't treat them well I feel