Can the EV reducing berries reduce any stat all the way back to 0 or do they just work 10 times like vitamins? Yup, you can reduce every EV down to 0, subtracting 10 EVs per respective berry use.
And if you defeat the same Pokemon twice in the same (link) battle, do you get twice the EVs? Since you don't gain Exp (and hence, you don't gain EVs) from a link battle, no. If you gain Exp from battle, you gain the associated (non-split) EVs, no matter how that battle Exp is gained.
Ok I have a problem. I was EV training a Torchic that I gave 10 Protein and 10 Carbos (or whatever the Speed booster is) and gave it Exp. Share. Then I had my Scyther (L63, leveled up twice) hold a Macho Brace and beat 3 Oddish (6 Sp.Atk EVs) and countless things that give only Attack or Speed EVs.
I kept track and it all added up to 510 and even my Scyther gained +13 and then +9 in attack during both its level ups, but the lady won't give me the Effort Ribbon for Torchic (now Combusken). I went back and killed like 5 Zubat and 5 Shuppet and she still won't give me the Ribbon.
NitroHeat It sounds like you are misunderstanding the relationship between Exp. Share and the Macho Brace. In your scenario, Torchic/Combusken is only receiving the standard amount of EVs after each battle (the points are assigned before the Macho Brace's effect is applied). When you defeat that Trapinch, Combusken is only receiving a single attack EV, even though Scyther is receiving 2. This means it would not be unusual for your Scyther to be fully EV trained way before Torchic/Combusken... Also check to make sure Combusken doesn't already have an Effort Ribbon... lol...
Ok so here's what I don't get. Vitamins are supposed to be 10 EVs, and every 4 EVs are supposed to equal one stat point. That should mean that using one vitamin on a given stat should raise the stat by 2 pts (with 2 EVs leftover), but it doesn't. 4 vitamins should be 40 EVs or 10 stat points. I've tried it on R/S/E/FR/LG, literally all of them, and I don't see it happening on any of them. Is the stat increase like IVs in that you can't actually see them on the stat page for your pokemon? That's the only thing I can think of. Anyone who can help would be good.
1. Stats aren't "live". They are only recalculated when a pokemon is withdrawn from a PC, or when it levels up. You can give it all the EVs in the world but they won't have any influence until one of these things happen.
2. The actual formula is probably more complicated, but essentially: ([Pokemon's level] divided by 100) * [the number of EVs that Pokemon has]. In English that means that at level 50, that pokemon is only affected by 50% of its EVs. If your Pokemon are at low levels, the EVs raise the respective stats by a much lower number, so you won't be able to tell they are there.