At what age and/or range does the brain stop developing . im asking because im 20 and turn 21 in march 2022 i have been smoking cigerattes and using nicotine on and off since i was 18 . i stoped at 19 and i havent smoke since march . will i be ok?

So you made the decision to stop smoking - good! Smoking for year can have some deleterious effects that may remain long term. You are young and your body naturally heals itself. The greatest problem is likely to be the way the lungs clean themselves. Tiny hair like cell projections waft and push dust and tar out of the lungs. This process is damaged by smoking. Exercise, rest well, no smokes

For a male, frontal lobe maturation at age 26. Effects of smoking essentially gone by 4-5 yrs after quitting