Lore

Lore was the name used by two Soong-type androids in the 24th century. (SS TNG (I Am Become Death))

Original Lore
Lore was a Soong-type android constructed by Doctor Noonien Soong circa 2335. While the most successful of Soong's androids to date, Lore exhibited antisocial tendencies which forced Soong to deactivate and disassemble him. Tragically, Lore was first able to contact a Crystalline Entity, which destroyed all organic life on Omicron Theta. Another aspect of his programming was his enabled speech to use contractions in grammar. Self-described as "perfect", Lore saw the colonists as envious and unable to grasp his "human qualities". Which were at one time ignored as "wild promises", made by Dr. Soong.

After deactivating and dismantling Lore, Soong set about constructing his brother Data, an android without destabilizing emotions. Lore's positronic net differed from Data's in that it had a Type-"L" phase discriminator, compared to Data's Type-"R". 

Lore was rediscovered in 2364 by the crew of USS Enterprise-D. Chief engineer Argyle and Dr. Beverly Crusher reassembled and reactivated the android, who then attempted to steal Data's identity in order to summon the Crystalline Entity to the Enterprise. One noticeable malfunction upon re-activation was a persistent twitch he corrected using the left side of Data's face. In Data's quarters, he privately asked him to consider the implications. Their Isaac Asimov-inspired technology "could reflect 1000s, or millions... of lifeforms of every kind". He was stopped by Data, who beamed Lore out into space. 

While in the void of space, Lore deactivated himself, fusing the matrix in his positronic brain. A version of Data from the 44th century, who has taken control of a Pakled vessel, eventually discovers Lore's body. Exchanging clothing with Lore, the alternate Data vaporized the body in front of the Pakleds in an elaborate ruse to take over Lore's place and prevent the rise of the Children of Soong. (SS TNG (I Am Become Death))

Second Lore
"Lore," originally Data, was an alternate version of Data from the 44th century who claimed to be the original Lore on several occasions against the USS Enterprise (NCC-1701-D). His ultimate goal was to discredit Soong-type androids. (SS TNG (I Am Become Death))

Specifications
At some point over the centuries, Lore had improved himself with various new internal devices. This includes a subspace beacon for initiating transport, when standard combadges were unavailable to lock on. It could also function as a transmitter link between himself and any other Soong-type android. 

As Data
Lore's history separates itself from Data's in 2367, when Data hijacked the USS Enterprise-D under control of Noonien Soong. With the original Lore dead, these events led to Data receiving his emotion chip and the death of Willie Potts.

After many years of loyal service, Data left starship duty to become an academic. Over the next few centuries, the deaths of his close friends (Jean-Luc Picard, Deanna Troi, Worf), his wife Tana, and many other crewmates and friends overwhelmed Data's emotion chip to the point that he routinely turned it off.

Eventually, he removed his emotion chip, only to discover after many more centuries that he grew emotions independent of the chip. Discovering he was now nearly Human, Data began to despise humanity and retired to Omicron Theta to live amongst the Children of Soong.

Beginning in the 32nd century, Data was kept under the watchful eye of Jaris on Omicron Theta. He escaped in the 44th century to commit suicide at the old Starfleet Headquarters, but was prevented by versions of Jaris and Damia from the 54th century.

In his brief encounter with Jaris and Damia, Data learned of humanity's fate and, after disposing of the two androids and losing an arm in the battle, used their timeship to travel to the year 24th century and revive Lore. Data believed that the continued existence of Lore would prevent the birth of the Children of Soong and the death of humanity.

Arriving in 2364, Data immediately took control of a Pakled ship and ordered them to search for Lore's body, helping them out along the way. After two years, the Pakled's discover Lore's body and bring it onboard. When Data discovers that the original Lore is destroyed beyond repair he develops a ruse where he convinces the Pakleds that he was Lore and he "killed" Data. He replaced his destroyed arm and loyally served with the Pakleds as "Lore." (SS TNG (I Am Become Death))

As Lore
In 2367, Lore answered the homing signal intended to draw Data to Soong's new laboratory on Terlina III. There, Lore posed as Data, took the emotion chip Soong had designed for his brother, and fatally injured the doctor. 

In 2369, Lore encountered a group of Borg disconnected from the Collective as a result of Hugh's sense of individuality. Lore established himself as their leader, ("the One", as he was referred to, unaware that the Collective hierarchy was composed of myriad Borg Queens), and directed them to attack Federation targets. This brought the Enterprise-D and Data to investigate, and Lore attempted to manipulate his brother by broadcasting emotions from the stolen chip. Data, with the help of Geordi La Forge, was able to overcome this influence, shoot and deactivate Lore. 

Data brought Lore to the Enterprise-D and disconnected his positronic brain. He kept it in a vault in his lab, isolated from his body, and designed the vault to self-destruct if it was ever tampered with. In 2371, when the Enterprise-D crashed on Veridian III, the vault containing his brain was damaged; the self-destruct system activated, and the brain was destroyed. The rest of Lore's body was unharmed, and as of 2374 was being kept in Data's lab on the USS Enterprise (NCC-1701-E).