R2-D2 served Queen Amidala and later Anakin Skywalker, accompanied by C-3PO. Unlike the golden protocol droid, R2-D2 never had a full memory wipe, so he was well aware of all events that happened around him.
A smart, spunky droid who would serve a multitude of masters over his lifetime, R2-D2 was never given a full memory wipe nor did he ever receive new programming, with these factors resulting in an adventurous and independent attitude.
However, the same could not be said for R2-D2, who never had his memories erased. While there isn't a canonical reason for this decision, the likely explanation may have been that Threepio was more likely to say something he shouldn't have.
However, R2-D2's memory is not wiped; as a result, R2-D2 is the only surviving character at the end of the saga who knows the entire story of the Skywalker family.
Why Yoda Didn't Remember R2-D2 (CANON) - Star Wars Explained
Why does Vader not recognize R2-D2?
Darth Vader acts like he doesn't even know C-3PO or R2D2. They were with him since he was a child. He did everything he could to forget his past. Also, his plating had been replaced many times, and protocol droids all look very similar.
Since Obi-Wan had been in hiding, going by the name Ben Kenobi, he admitted that he was actually Obi-Wan. However, he denied owning R2-D2, acting as if he was not familiar with the droid.
Darth Vader's true identity as Anakin Skywalker was a highly guarded secret, known only to a select few individuals including Palpatine, Obi-Wan Kenobi, Luke, Han, Leia, R2-D2, C-3PO, Master Yoda, Bail Organa, Ahsoka Tano, Darth Maul, Grand Moff Tarkin, Grand Admiral Thrawn, Jocasta Nu, Ferren Barr, Verla, Reva, ...
With the fate of the galaxy hanging in the balance, C-3PO reluctantly agreed to have his memory erased so the runes could be read. Fortunately, this mechanical amnesia was only temporary, as R2-D2 had backed up his friend's memories before C-3PO left.
secondly, in Legends, R2 was given programming that actually restricted him. from sharing any information with Luke or Leia. about their parents or relation to one another. this was all part of the plan. to conceal this information from the twins.
He's had several owners over the course of the movies. He is initially property of Naboo - an emergency repair droid on the queen's ship. The R2 appears to become Padme's property although Anakin seems to have a “personal” connection with him.
As has been noted in several instances, Artoo has never had a full memory wipe, enabling him to retain his recollections of everything he saw and heard over the decades. This includes his first meeting with Padme Amidala, a nine-year-old Anakin Skywalker, and C-3PO himself during the events of The Phantom Menace.
in the Dark Horse comic series star Wars Tales, which is now part of legends, it's revealed that Darth Vader did recognize C. 3PO on Cloud City. when 3PO was shot by Stormtroopers, his parts were brought before Vader. because the Imperials thought he could hold valuable.
For starters, C-3PO physically resembles just about every other protocol droid. There's no real defining feature that sets him apart from the other models. Additionally, the last time Owen saw C-3PO, the droid had silver coverings, but in A New Hope he's obviously gold.
The lack of recognition could have come from an old man simply not remembering the passing droids of his youth. Lastly, Owen didn't seem the sentimental type to form any emotional attachments to droids. Being a practical man, he viewed them as tools to be used and replaced when they no longer functioned.
The base assumption of why Obi-Wan doesn't remember R2-D2 -- in light of the prequels -- is that Obi-Wan is feigning ignorance in A New Hope to downplay the importance of the droid's arrival.
At the end of Star Wars: Episode III - Revenge of the Sith, C-3PO's memory was wiped, allowing him a fresh start by the time A New Hope begins, but R2-D2's memories remained intact, which is why many fans wonder why he didn't tell Luke the truth about his family history, but he might have not done that because he didn' ...
After Ashoka and Vader face off in season two (the season finale, I believe), Ashoka has a moment of realization, and Rex has a similar, though less prominent moment like that in a later season. Unfortunately, Rex and Vader never meet again though.
According to Imperial Estimates in Star Wars Inside #87, only about 100 of the Jedi survived Order 66. Most were subsequently hunted down and killed in the years following the Great Jedi Purge.
To understand why R2-D2 does not speak Basic, we must appreciate that his primary function doesn't necessitate it. Instead, he communicates through beeps and boops, efficient for his role as a starship repair and navigational unit.
Towards the end of the war, Anakin turned to the dark side and Padme died so her friend, Bail Organa took the droid as well as R2 when he took her daughter, Leia. C-3PO has his memory wiped unlike R2-D2.
