Vampire Questions

Vampires, loved by middle aged gamers and teenage girls, yet their screen existence has multiple "weaknesses" which make no sense whatsoever

Ye olde wooden stake, famed for its ability to kill vampires when driven through the heart, yet why must they be stakes? Surely wooden spears would be more efficient, or must they be in a stake-y shape, what if a stake isn't stake-ish enough? Would it cease to work?

The sun, Harkon's greatest enemy some movies and games depict them dying upon immediate contact with sunlight. Yet others show them being weakened or severely hurt by its presence, yet why does it burn them? Is it their pale skin? Are black vampires immune to the sun? Would sunscreen be enough to ward off their bright scourge?

Healing, healers and potions are a necessity for any brave adventurer, yet for some strange reason vampires (and other undead) are injured by healing? Why would this be so? Sure, they may be dead and have nothing to heal, yet that does not mean that they should be injured by health?

Holy water, the saintly vampire ward. Water blessed by saints and priests has vampire killing properties, but what if one was to splash regular water onto a vampire and THEN bless it, would it still work, then would it be the blessing not the water which kills the vampires?

Puppy Tax, her name is squishy and she hunts vampires, we haven't seen any vampires so shes obviously doing her job