No the Adventurer's Blessing is not available on Hardcore or Retro PVP, just on Open PVP will the Adventurer's Blessing be available. I just created 3 characters to test this out. I wanted to paste some valuable information about this blessing from the official Tibian Manual:
Adventurer's Blessing: Characters on open PvP game worlds up to level 20 are automatically protected by the Adventurer's Blessing. You can easily see if your character is protected by this blessing by the little ankh shown in your inventory. Further, your character's inventory will be displayed in yellow. If your character dies in a PvP fight being protected by this blessing, your character will not lose any items, experience and skill points. But beware! As soon as your character attacks another character first or reaches level 21 for the first time, the blessing will be lost for good.
Any items lost upon death will remain with the body of the deceased character and can be looted by any player who happens to find it. In case a character has lost its bag or backpack after death, it will receive an empty bag in the container slot.
Characters up to level 8 will never lose items upon death.
Source: https://www.tibia.com/gameguides/?subtopic=manual§ion=characters
Clicking on this little ankh , opens the Blessings dialog. Here you can see by which blessings your character is protected. Moreover, you have the option to go right to the Store to purchase missing blessings. You can also check how blessings and a possible promotion or Premium status influence the penalty for your next death. If you click on "History", you can check when and where you gained a certain blessing and for which death it has been used up.
- If the little ankh is displayed in grey, your character is not protected by any blessing.
- If the little ankh is displayed in green, your character is protected by all available regular blessings and the PvP blessing "Twist of Fate" provided it is available on the character's game world.
- If the ankh is displayed in yellow, your character is protected by at least one blessing. If your inventory is additionally displayed in yellow, your character is protected by the Adventurer's blessing. However, this blessing is only available on Open PvP game worlds. If your character dies in a PvP fight being protected by this blessing, your character will not lose any items, experience and skill points. But beware! As soon as your character attacks another character first or reaches level 21 for the first time, the blessing will be lost for good. Then your inventory will be displayed normally in grey.
Source: https://www.tibia.com/gameguides/?subtopic=manual§ion=interface#blessingsdialog