Yeah NPCs on the route (the other trainers, everytime they turn, they advance the PID, which controls shininess).
Yeah... Maybe you can abuse your legendary mascot, but that's painful. You battle 2 nubs back to back after capturing your legend. So you have to lose to the first 1 to check the legend's nature, lol. :P
Right, but the program searches using ranges like 19-23 atk, 14-15 def, 21-26 spatk, etc. Of course, when you are abusing wilds or abusing eggs, you won't get accurate ivs. there's no point in checking your adjacent seed. Just keep trying and if it results as 26-31 in every stat you pretty much got your target... .-.
I didn't say you bring it into a battle subway battle; I said talk to a trainer and he evaluates Ivs.
Yeah it's possible; I can't because other moving trainers (i.e. NPCs) turn and make advancing difficult.
Lol... Don't try to rng abuse until you are at least in Victory Road.
I haven't used an AR at all during non-cgear abuse. It is not necessary. Metalkid's IV calculator is fairly accurate: here
The IV judge is in the Battle Subway. He looks like an ace trainer. He will tell you the overall IVs as well as any flawless IVs all in the first interaction (no more talking to him 5 times, yay). The Hidden Power Judge is in the Mistralton PokeCenter. He's near Nurse Joy.
I explained how to find the MAC on the older DS in this post: here