Are the 3 idiots in the Recruitment arc the same ones in the beginning of the series?
As ʞɹɐzǝɹ mentioned, they are not the same three idiots.


The first set of three idiots had no idea that Osamu was in border. On top of this they are not in border either. You can check this in episode 01 where they run from the neighbors rather than trying to fight using triggers (normal/training).
The second set of three idiots basically replace the first set since the first set is never mentioned again. The second set of three idiots become part of border as class C agents—trainees. You can tell by the white/orange uniforms.


While all six of them are idiots, they still play different roles. The first three being Osamu's bullies, the second three acting as superiors of Osamu.

You can check their personalities and appearances via episode 01 for the first set and episode 17 for the second set.