When a Devil Fruit is bitten (even once), it loses its powers PERMANENTLY or until the person who bit it first dies. When the person who first bit it dies, the Devil Fruit returns to its normal state, so someone else can get the power.
Once a Devil Fruit user dies, the fruit reincarnates into a nearby fruit and can thus be eaten by another person, meaning a Devil Fruit power can have more than one user and fans have seen a handful of such fruits already.
After the first bite, it becomes a normal fruit and doesn't grant powers to a second user. A devil fruit can't be shared between two or more people as the first person to eat the slice will get the powers immediately. They taste very bad in general.
Can Luffy take second devil fruits or not? No. At present the only person who has, somehow, managed to acquire two devils fruit powers is Blackbeard, and no one knows how he did that. Normally if someone eats a second devils fruit, it'll poison them and they'll die.
If consumed by a human, this fruit will have no effect on them other than taking away their ability to swim. Oda said in a joking manner that a human who ate this fruit might become "more human-like" or find their "true spirit".
One Piece's Wano arc revealed that Luffy actually has the Hito Hito no Mi, Model: Nika Devil Fruit, and it is something special. One Piece's Wano Country arc revealed quite a lot to the fans about the story of Joy Boy and, at the same time, added a lot of depth to Luffy's character.
Over the years, he has come a long way and become one of the strongest pirates on the seas. Zoro has attained terrific strength, but he does not rely on a Devil Fruit at all.
Zoro can eat 3 devil fruits.
Blackbeard is the only character in One Piece with two Devil Fruits. How did he do it? Marshall D. Teach, better known by his epithet, is arguably the most dangerous living pirate in One Piece.
Every personality can have one fruit. So luffy can't eat another devil fruit and stay alive. The symbol of blackbeard have 3 skulls, so in the future he might eat a third devil fruit. Or probably because he has a sleeping disorder.
The Supa Supa no Mi is a Paramecia-type Devil Fruit that enables the user's body to gain characteristics of a steel blade to attack opponents with, making the user a Fullbody Bladed Human (全身刃物人間, Zenshin Hamono Ningen?, VIZ: "Human Sword"). It was eaten by Daz Bonez, also known by his Baroque Works alias Mr. 1.
The Daishou Daishou no Mi is a Paramecia type Devil Fruit eaten by Nefertari Vivi a month after the Straw Hats departed from Arabasta. It grant's the user the ability to change their size.
All Devil Fruit eaters lose their ability to swim after consuming the Devil Fruit. It's not just a loss of muscle memory; entering a body of water saps them of all energy. Even entering a bath can drain a Devil Fruit eater of energy and prevent them from using their abilities.
If an animal ate a Zoan-class Devil Fruit that is exactly the same as their original species (such as a human eating the Human-Human Fruit), it would result in a complete waste, as they gain no transformation whatsoever, yet acquire all the typical weaknesses of Devil Fruit users.
One of the many snake Fruits seen in One Piece, the Yamata no Orochi version is considered to be the rarest out of them all. It was eaten by the Shogun of Wano, Kurozumi Orochi, and it grants him the ability to transform into an eight-headed serpent, each head having its own personality.
It is possible that Blackbeard consumed the Inu Inu no Mi, Model: Cerberus, a Mythical Zoan-type devil fruit. Since Cerberus is known for having three heads attached to the same body, it would explain how Blackbeard managed to eat two more devil fruits, one for each head.
No, not even close. Luffy's devil fruit is among the strongest devil fruit in the series. It's the ancient Mythical Zoan-type Devil fruit call Hito Hito no Mi, Model: Nika that allows the consumer to gain Nika's abilities.
In a Water 7 filler episode, Sanji finds another hint of the All Blue's existence. Salt is brought by the Aqua Laguna from all the seas and Sanji compares it to the All Blue. It is shown to be such a good seasoning that a small amount in food is enough to outclass even his own cooking.
Hito Hito no Mi, or human human fruit, is a zoan type devil fruit. This fruit's effects on humans are unnoticeable because the effect itself is turning the user into a human. If Sanji ate this fruit, the only ability he would gain is a swimming disability.
In the two-year time skip, Zoro trained under Dracule Mihawk, popularly known as Hawk Eyes Mihawk. One of the popular theories is that the scar on Zoro's left eye is a training mishap. Many believe that Zoro lost his left eye during his training in some sort of accident or battle.
The Sakana Sakana no Mi, Model: Shark(速いチーター Fish-Fish Fruit, Model: Shark) is a Zoan type Devil Fruit that grants the user the power to transform fully or partially into a Shark. The fruit was eaten by Zoy.
Points: Zoro 1, Law 0 Devil Fruit Roronoa Zoro is a very powerful character. He is known as one of the most powerful characters in the series and one of the series' best swordsmen; he is, by all means, probably going to surpass even Mihawk in the future.
Enma is the strongest sword possessed by Zoro of the Straw Hat Pirates right now. What is Zoro's weakest sword? Sandai Kitetsu has to be the weakest sword Zoro has used until now in the One Piece manga and anime.