The four stars on the New Zealand flag represent the Southern Cross constellation, Crux.
The Stars on the New Zealand flag represent the Southern Cross Star constellation which is only visible in the Southern Hemisphere, and south of latitude 30 degrees in the Northern hemisphere. The formation actually omits the fifth star in the constellation.
A cluster or star cluster
It is a constalation
There are several blue, white and red flags, the Union Flag (Union Jack) is blue , white and red flag of the UK, as is the Australian flag, the New Zealand flag and the US flag which also known as the Stars and Stripes.
The name of the Philippines flag is 3 stars and a sun. The Filipino flag was adopted on June 12th, 1898.
Nebulae
A "cluster".
The collective noun - cluster
The smallest galaxy - a dwarf galaxy - will contain stars upwards of 30 billion stars. You are thinking of an open cluster, which as the name suggests, is a cluster of stars, not a galaxy. An open cluster is a group of up to a few thousand stars.
Constellation or "asterism". The difference is that "constellations" are officially recognized by the International Astronomical Union, while an "asterism" is any other pattern or grouping of stars.
The American flag is commonly referred to as the "Stars and Stripes" or the "Old Glory."
It is the Stars and Stripes.