If it's a fine cashmere sweater, why not wear it alone without shirt or t-shirt. I know the big thing in women's fashion this year is layers, but the masculine body benefits from a more minimalist silhouette.
Not a good look. You'll look like Simon off American Idol. Not a good look. There are good nipples (female) and bad ones.
As someone who's been known to wear a lightweight turtleneck under a collared shirt under a sweater, that hurts.
Not a good look unless you are, in fact, Alan Ginsberg. I suspect that you are not. An untucked, soft collared shirt (either buttoned down or not) under a sweater is fine, just don't pair with chinos unless you want to look... bad. A turtleneck under a sweater is okay if you are Starsky. Not okay if you are Hutch.