1)-R2 met Obi Wan in Ep1 for the first time, then he met him again 10 yrs later in Episode 2, to me R2 is a droid and having met him twice yrs apart i would guess that he would remember Obi Wan in episode 4, yet Obi Wan acts like he never seen him before, why is that?
How many droids are there in the Galaxy? Millions.
The Star Wars Galaxy is filled with droids. They're everywhere. There are mechanics, food servers, medical droids, probe droids, battle-droids, protocol droids, pilots, assasins, there are droids who work in libraries, droids who fix broken windows, every job you can think of there is some kind of droid to do it.
So for people in the Star Wars Galaxy, droids are no big deal. They are around all the time. They go un-noticed.
Watch AOTC and you'll see this. R2 is usually there but he's in the background out of the way.
Obi-Wan doesn't spend much time with R2. In AOTC he spends more time with R4. It's not hard to imagine that Obi-Wan would forget about ONE particular droid in a galaxy full of them. Especially when R2 doesn't look any different from any other astro droid. Think about the first time we see R2 in TPM. He's in a line with 5 or 6 identical droids.
Droids in Star Wars aren't like pets. They're more like T.V's, or Microwaves. They do a job and when they brake, you get a new one.
2)-when Luke is training with Yoda Obi wans gost appears and tells Yoda that he was his Teacher the one that trained him when in fact was Qui-Gon, Is it a mistake made by GL?
Yoda teaches all Jedi when they are children (like we see in AOTC), then if they are good enough they become a PADAWAN and are given a Master.
Yoda tought Obi-Wan and then when he reached a certain age he was given to Qui-Gon.
3)- Leia is reffered thru the whole movie as princess but in episode 2 Amidala is no longer a Queen but a senator, why is Leia called a princess if shes the daughter of a senator?
This will have to be explained in Ep3. Like others have said, it's to do with Bail Organa and Alderaan.
4)- How come 3po doesnt mention anything about Anakin/Vader when Anakin was his maker and being another droid should have known all along who he was, but is like he had no clue, being a droid he should have made the correlation,
Again, something that has to be explained in Ep3. 3PO will probably have his memory erased. We know this happens because Owen tells Luke in ANH to take R2 to Anchor Head and have it's memory erased.
I read somewhere that some droids in Star Wars have to have their memory wiped because after a while, they start to develop personalities and become more human.
5)-does anyone knows whos Anakin father was?
Anakin was concieved by the midi-chlorians or the force. Like Ush said, it's not meant to be a Christian thing.
All through history and mythology, the hero has some kind of "special" or "unusual" birth. Alexander the Great, Hercules, Plato, Julius Ceaser etc. It's not a "virgin birth" because who's to say that Shmi is a virgin?
All we are told is that he was born without a father and then the Jedi figure out that he fullfills an ancient prophecy and was concieved by the force.
6) Don't know.