I skimmed over most of this because it's just :words: but anyway, there is an excellent blogpost around (although it's down right now) about the differences between grain and noise. Mosquito noise, dirt, actual noise, and whatnot are all characterised by off-colour (usually) blocks. The difference is in the size and location. Mosquito noise tends to cover a larger portion of the image but is very small, often just 1 or 2 pixels. Dirt can be either film dirt, or on digital footage that kinda crap you get in between 2 massive chroma differences or close lines, especially on the points of hair in anime. This is what you're seeing here. Regular/actual noise tends to cover flatter blocks of colour and is just off-colour pixels, usually caused by poor quantization and/or MPEG-2. Early digital anime (circa 2004-2006) has a lot of dirt, especially on hair and edges of bright clothing against blue or grey. Might have lots of actual noise too but that is more prevalent in MPEG-2 transport streams and other bitrate starved forms of that codec. Mosquito noise tends to happen on film or when incorrectly applied grain is quantized. It is very small though and not all that common, the term is usuallyused for dirt rather than actual mosquito noise, but it is important to know the difference so you don't trash it with the wrong filters.
tl;dr dirt is on edges of hair and bright colours, mosquito noise is almost impossible to see, other noise is on flat colours, grain is good for you, eat your vegetables