Is ChaCha12 considered 256-bit secure? ChaCha20 is considered 256-bit secure (no attack faster than brute force).  However, the best known cryptanalysis that I know of is on ChaCha7.

That gives ChaCha20 a rather large security margin (much larger than, say, AES-256).  Is ChaCha12 still considered to be 256-bit secure (as in "considered usable when top performance and 256-bit security are needed, no HW AES support, and ChaCha20 is too slow")?
Yes, the best attack still seems to be on 7 rounds. Namely, "Improved Key Recovery Attacks on Reduced-Round Salsa20 and ChaCha" shows a $2^{246.5}$ time attack on the 7-round variant.

So even the 12-round variant has a decent security margin – better than AES-256 had when standardized, much less currently.