Is the north star a planet?

No.

The Sun is the brightest star (relatively, due to distance) in the sky.

The moon. Earth's satellite is brighter than Venus.

Venus is a planet, not a star. Venus is, however, the brightest planet in the sky followed by Jupiter and Mars.

The apparent magnitudes of several celestial objects is:

• Our sun: -26.74
• A full moon: -12.92
• Venus: -4.67
• Jupiter: -2.95
• Mars: -2.91
• Sirius: -1.47 (the brightest star after the sun)