I think Sweden is pretty similar to Finland in this regard. So 13 year old can do this type of office work, but it is not allowed to impact school and only for half of the holiday length. Also some other limitations on length of work day.

Intern, not employee. Funnily enough, it's allowed to let them work for free, but not for money.

It's like chess grandmasters - they just keep getting younger and smaller!

teenagers shouldn't be hired until they completed high school, education is more important, I regret after working full time as freelance web developer, I didn't consumed much knowledge, I think i wasted time.