>>501646391. As mentioned previously, Giant evolved into a Golurk in the same battle where she got Sparky. At this time the two were still very much at odds with each other despite a handful of moments of cooperation in the past, and Giant showed no interest in battling for Anya at all. But Anya made it clear that she was going to get Sparky with or without Giant's aide, and the sight of an 11-year-old kid running straight towards a giant Celesteela was enough to get him to cooperate. Anya's unyielding determination in the face of an unstoppable opponent greatly impacted Giant's perception of her, and in the face of a giant foe, the only thing you can do is get bigger.
2. Not yet, but there's always a lingering doubt in her mind. The contents of the letter that set Anya off on her journey in the first place were vague about what she needed to do, so every so often she wonders if becoming a stronger trainer is actually bringing her any closer to her goal. She has nothing to indicate she's making progress towards seeing her mom again, which makes her worry. But a strong team is a good thing to have anyways, and will only open more doors for Anya to search through. She'll never give up on looking for her mom, but the method to getting there is... Questionable.
3. Anya doesn't like the idea of reserve Pokémon. The Pokémon on her team are very personal to her, serving like family and companionship at a time when she has nobody else. Having Pokémon that are left in storage would be like ignoring a member of her family; and she can't stand for that.
I might get to the others later