Beer–Microbreweries and Hashgachot

Dear Rav,

You year-round list says, “All 100% Beer is OK.” However, when I look up various lists by major kashrut agencies, they have a list of brands to avoid.

One particular example was Sierra Nevada Pale Ale, where one site said it was because of chameitz she’avar alav happesach. Is this a valid concern?

And are there issues with purchasing from a local microbrewery, as long as you avoid grape-derived flavorings and milk-derived flavorings?

One final question: beers that are flavored with seemingly-neutral ingredients, like spices, pareve chocolate, or fruit; do they need hashgachah or no?

Thank you so much,

Eliran