About cards and packs
Click on the image of the pack or simply hover over it. The field "immutable attributes" contains the description and probability of getting a certain card. Please note that if it says "contains unique cards", it means that inside there are only cards with a multiplier of x1.1. Consequently, if it says "cards" (without any prefixes), then there are only heroes with a multiplier x1.0 inside.
To unpack, you need to follow one of the links:
Yes, all information on the card is recorded. A display of the accumulated experience will soon appear on the marketplace, and unfortunately, this is not yet visible when selling on Atomic. When you enter into the game a card that has been upgraded before, the level of accumulated experience will be displayed on the card page (in the inventory).