Is this sentence correct?

Question

If young people play sports for a long time, it will be a good habit when they has grown up.

Answer 1

If young people play sports for a long time, it will be good when they grow up.

Answer 2

Sports would be a good habit for grown people if they had played for a long time as youths.

Answer 3

The grammatical error is that "have" agrees with "they". There's also a problem because there's no real antecedent for "it". What is "it"?  Use a pronoun for something you mentioned in the first part.

If young people play sports for a long time, they will have a good habit when they have grown up. 

Answer 4

The sentence is grammatically correct. I would suggest:  "When people play sports as youths, they often develop an adult habit of remaining active."

The wording of your sentence suggests everyone who plays sports develops a habit of playing sports as an adult.  This is not necessarily the case.  They may not carry the habit into adulthood, and they may not continue playing sports.

Answer 5

Young people participating in team or individual sports, will give them vast experience in adapting to stressful situations and enhancing their ability to cope with human nature.