ive been playing halo 3 a little after its release, and I haven’t received recon (I didn’t do the vidmasters because they were kinda hard and I didn’t have the time) and so if you could just give me a chance to receiving recon, id be pleased 
If you didn’t get it before you won’t get it now. Support for Recon has been discontinued.
Quite frankly if you didn’t get it when it was available for two years then I’m not sure what to say to you. 
Your best bet at this point is to wait for the MCC to come out and see if there’s a way to unlock it on there, as for the Xbox 360 version of Halo 3 - There’s no way to get it now, sorry OP.