Yes. For Korean albums the sale counts on the Hanteo Charts. For Japanese albums the sale counts on the Oricon Chart.

Yes - all items are legitimate. The origin of the product is mentioned on the item's description.

I can assure you that the albums that I've purchased from them have been legitimate (my most recently purchased one was from a month or so, and I received it in the mail).

Yes. I have ordered Girls' Generation & T-ara albums in the past, & currently working on my LOONA stock. All albums legit, sealed, with authenticity seal, & purchases count towards real time Hanteo & Gaon charts.

Absolutely, I have been buying from them for 10 years.

Yes which is why price somewhat higher than some places I've been in Taiwan.