I know someone who is applying for their ARC. However, they have a few charges as a juvenile, including:
2 GTA
2 receiving stolen property misdemeanor
2 receiving stolen property felony
And 1 first degree burglary that was dropped to a second degree
However there record is sealed.
Knowing this, will they face problems when applying for an ARC? If so, how can they overcome these problems?
Welcome @Guitbk too zee fouruhm.
While I don’t have the answer, I hope your friend has changed his youthful incorrugibilty with thievery and is now trying to find a new path to a better life.
That in and of itself would be commendable indeed.
Taiwan will certainly offer a life-altering experience, no matter what.
Can they check with AIT?
If your juvenile record is sealed then generally it will not affect you. It only comes back to haunt you if you’re applying for a job in law enforcement or for the government (two groups who can always find a way to access your records), or in the case of those GTA charges, an insurance company might be granted access when you’re applying for car insurance.
Complicated things like this can sometimes be sufficiently explained away by a personally signed letter. You’ll have to consult a lawyer for more information.
I should mention — if you did, in fact, get every single thing on your juvenile record sealed/expunged, and you don’t have any other criminal charges in adulthood, you can legally say you have never been arrested. So you might not have to even address the issue. 
AFAIK “sealed” means “sealed.” I don’t know if it’s even accessible unless you’re applying for a job with the federal government in the US (which your friend isn’t).