Since no information was given in their API documentation.... Is it possible to make a search using the BestBuy API, giving as parameter the UPC(barcode) and retrieve information about the product such as price,pictureurl,discounts, etc?
Yes, it is possible. The documentation at https://bestbuyapis.github.io/api-documentation/?shell#search-by-all-attributes-and carries a lot of the examples that you're looking for.
For your specific request, you'd be looking to do a query like
https://api.bestbuy.com/v1/products(upc=12345)?format=json&show=sku,name,salePrice&apiKey=YourAPIKey