No
Juvenile record, or not, that's a pretty serious charge. You will have to check with your state's licensing agency for this profession to determine if they will issue you a license.
A criminal record
Yes, it can. Juvenile records are only sealed from the general public - NICS and law enforcement agencies can still access them.
If you are 21 and have no criminal record there is no requirement to have a carry license however you do need one is you wish to carry concealed.
No! You absolutly do not have to divulge your juvenile record.
Yes. Whether you'll be able to find employment or not, is a different matter.
Yes! When you turn 21 and some states 18 years old your juvenile record is wiped clean. You get a new start on life and make the best of it. O.K.
Once the juvenile reaches the age of adulthood, their juvenile record should become automatically sealed to the public. I am not aware of any specifc procedures for expunging a juvenile's record while the individual is STILL a juvenile.
Yes, your drivers record is a lifelong compilation of of your driving history starting when you first receive it.
No
No. Your Driver's License record is running history of your driving history throughout your life and, unlike juvenile criminal offenses, does not "go away" after you turn 18.