is completely normal & doesn't have any bad effect to the body and mind.
2. Size of the penis is genetically determined & it cannot increase after a certain limit.
3. Nocturnal penile erection is normal phenomenon
4. Penis is darker than rest of the body due to increased pigment content.
One more thing...avoid consuming any over the counter medication
which claim to increase the size of penis or improve performance...it may be harmful.
Wishing you a Healthy Life.