Here is an app to help with your instagram question https://apps.shopify.com/instafeed
and with pinterest have you tried to click on the product you wants then look on the right side of the screen where you can pick where you want to product to show and click pinterest.
Thank you for the app but it's not working as I mentioned. I want to add all of my product's photos to my Instagram account not opposite. And the Pinterest option you're talking about is the Shopify Pinterest Channel from Shopify, which isn't supported for my store because my store isn't from the US. But thanks anyway :)