Ok, FAQs aren't helping so I need your help :_ (
Beware, spoilers!!

Battle Network 2:
I need bugfrags to buy the Attack+30 chip and I can't find any anywhere, I know there are exactly enough bugfrags to buy everything from the bug trader but I really can't find them and, as I said, FAQs aren't helpful on that. Anyway, since thanks to the Gospel Duplication Trick I just need one I'd like to know if any of you remember ONE hard-to-spot bugfrag, like the one hidden behind the slope in Undernet2, to get as many as I need from that one. Thanks.

Battle Network 4:
Is it normal that Duo is so goddamn impossible? I can't even take out 1/2 of his health! I need strategies and useful chips against him. Thanks again.

BN2 bugfrags can be a pain alright, I'm usually pretty thorough, and I still manage to miss one or two by the end and have to go through the whole list to find out which ones I forgot. Almost all the BFs are hard to spot as a rule, so I couldn't really suggest any. My advice is to just go through the Bugfrag locations FAQ systematically until you find that one you need.

As for Duo, obviously any ground-based attack is right out. It's been a while since It's been a while since I've played, but it looks like I still have the same Duo folder set up. It's got Vulcans, Spreaders (for H-Burst), GunDelSols (best used separately rather than as PileDriver, and in tandem with Invis), Tornados, SideBamboo, Recovs (Roll Soul is good for this if you're playing Red Sun), FastGauge, Invis, AntiDamage, Guardian, FullCustom, Atk+30, Windman, Videoman, and Red Sun. All those things work great on Duo.

In Blue Moon (yeah, I have both copies for some crazy reason) it looks mostly the same except with Bass Another, the chips for a BodyGuard Advance, and SuperVulcan. I think the souls of choice in BM are Number and Wood.

Thank you, but where can I find that Bugfrag locations FAQ? It's not on GameFAQs at least.

I thought there was. From the looks of things, they just list vague areas, but I guess the specifics are what MegaBoy's maps are for.

Yay! I found the bugfrags! (still haven't attempt to defeat Duo, though)

But now I'm having trouble with Bass SP, he regenerates his aura too fast, and good multi-hit P.As like Gater or Bodyguard don't work since it's now a 150 aura. What's a good strategy against him?

Use Gater with a bunch of Attack +'s.

Hmm... I don't remember what exactly I did but I would use chips above 150 for the sole purpose of destroying his barrier, then make sure you also have a multi-hit PA to nail him immediately afterwards. VarSwrd should be a good help when you use the triple slash combo because it's strong enough to destroy the barrier AND deal 320 damage. Always wait until your custom gauge is full when you want to remove his aura.

Now, when you go up against Bass DX where he has a 200 HP aura, you're probably going to have to use one-hit PA's just to get his aura away. Otherwise it's the same strategy.

Can't do that. You can only send 5 chips per turn, Gater uses 3 chips, and there's only one Atk+30 so even if I used two Atk+20 that wouldn't be enough (Gater hits deal 100 damage).

Thanks, Makenshi, I don't know how did I not think about using a chip to break it after the custom bar refills again xD I'll try using ProtomanV3 so it should work against a 150 and 200 aura.

EDIT: Yeah! I completed the Library.