Hi,
If you have the "Characteristics dynamic display" setting activated in the HikaShop configuration and you have at least 2 characteristics in your product, the characteristics won't be preselected and you'll have to select them before accessing the information of the variant.
Still the images and description displayed will be the ones of the default variant if any.
There is no mechanism to display the data of the main product by default when you access the product page. That would require some customization of the view files displaying the product details page