I've been a Star Wars fan ever since I can remember, anything.... really.

I just threw in A New Hope, and am at the part where Luke Skywalker is asking his uncle about Ben Kenobi being Obi-Wan.

I stopped it to ask a question that I have wanted the answer to for a long time, now.

Firstly, how does everyone understand R2? And all the other languages out there. Was it just for convince purpose for the movie, or is there an actual reason that I'm missing?

And secondly, I understand at the end of Episode III Bail Organa had both R2 and C-3POs memories erased, but I was curious as to why Obi-Wan didn't remember them.

Luke and his Aunt/Uncle had worked with plenty of droids before, so they probably picked it up earlier.

IIRC, 3PO was the only one who got memory-wiped by Bail, R2 still knew everything, which would've been why he remembered Obi-wan and 3PO didn't.

As for Obi-wan, I'm guessing he was playing dumb just to be safe.

Luke and his Aunt/Uncle had worked with plenty of droids before, so they probably picked it up earlier.

 

IIRC, 3PO was the only one who got memory-wiped by Bail, R2 still knew everything, which would've been why he remembered Obi-wan and 3PO didn't.

 

As for Obi-wan, I'm guessing he was playing dumb just to be safe.

Actually R2 got memory wiped too, all droids got frequent memory wipes, but Princes Leia inserted a disc/something (plus her message to him) which contained mission details, That's why R2 knew about Obi-Wan and Luke divulged his approximate location. C3PO however was elsewhere at the time, and so didn't get the mission, he just thought R2 was acting up.

Actually R2 got memory wiped too, all droids got frequent memory wipes, but Princes Leia inserted a disc/something (plus her message to him) which contained mission details, That's why R2 knew about Obi-Wan and Luke divulged his approximate location. C3PO however was elsewhere at the time, and so didn't get the mission, he just thought R2 was acting up.

r2 didnt get his memory wipped it was just "protical droids mind wiped". r2 never had his mind wiped since leaving naboo. and konobi owned r4 not r2

Actually R2 got memory wiped too,

R2 never got a memory wipe. In the Dark Nest novels, he actually plays scenes from ROTS for Luke, in which Luke finds out his mother is Padme. R2 could not do this if he'd been wiped.

It seems most people who worked with droids understood the language.

R2 never gets his memory wiped. He's the lorekeeper for the entire series.

Obi-wan said "I can't recall ever owning a droid". He often answered questions in a way to not reveal too much to Luke all at once. His statement is true, he never did "own" a droid, and definitely not r2. Technically Jedi don't own their droids, the order does.

Firstly, how does everyone understand R2?

Luke doesn't actually understand exactly what R2 is saying. Only 3PO knows exactly what R2 is saying. Luke (and others) can guess R2's intent based on whether the sounds he makes are "positive" or "negative", etc.

As proof that Luke does not understand him verbatim, I'll point you to Empire Strikes Back. Luke and R2 just got to Dagobah, R2 tweedles something to Luke, and Luke replies:

"If you're saying coming here was a bad idea, I'm beginning to agree with you."

like other said R2 doesn't get his memory wiped... which means he is kinda of a jerk. R2 knows everything, he is there when Luke is born, he knows who his father and mother is, he knows who his sister is, yet he says nothing.

However Obi wan not reckonizing or even Owen not reckonizing either of them is a bit of a plot hole. There is no way the guy who owned C-3po for years and who put that metal skin on him wouldn't know him.

Luke doesn't actually understand exactly what R2 is saying. Only 3PO knows exactly what R2 is saying. Luke (and others) can guess R2's intent based on whether the sounds he makes are "positive" or "negative", etc.

 

As proof that Luke does not understand him verbatim, I'll point you to Empire Strikes Back. Luke and R2 just got to Dagobah, R2 tweedles something to Luke, and Luke replies:

 

"If you're saying coming here was a bad idea, I'm beginning to agree with you."

While being in the X-Win, when R2 "talks" Luke can see what is R2 saying in his screen. See that scene again.

Regarding languages:

In the first film Luke does not understand R2-D2 (C-3PO has to translate everything) and Chewbacca. By The Empire Strikes Back he has sepnt time with R2 and Chewbacca and understands both of them.

For your second question:

In-universe answer: R2's memory was not wiped and Obi-Wan, typically playing things close to his chest, does not reveal that he knows who R2 is as it might lead to uncomfortable questions about Anakin.

This universe answer: While Lucas said that the only characters who would appear in all 9 of his originally planned films were R2 and 3PO, I'm not certain he knew at that time that Ob-Wan and R2-D2 would know each other.

However Obi wan not reckonizing or even Owen not reckonizing either of them is a bit of a plot hole. There is no way the guy who owned C-3po for years and who put that metal skin on him wouldn't know him.

What about Darth Vader not really acknowledging threepio? He built the droid when he was a kid.

 

However Obi wan not reckonizing or even Owen not reckonizing either of them is a bit of a plot hole. There is no way the guy who owned C-3po for years and who put that metal skin on him wouldn't know him.

One protocol droid may look much like another; TC-14 looked just like Threepio, for example. I mean, what are the odds that the very same protocol droid you saw flying off before the War with a Jedi and a Princess (over 20 years ago) would be captured by Jawas and sold back to you? There must be thousands of them in the galaxy, after all.