1.Hollow icons or icons with transparent background should be avoided.
Correct
Icons should not be hollow. Background should not be transparent.
2.The same design is expected to be adopted by icons of all the three sizes.
Correct
Varied designs should not be adopted for icons of the three sizes.
3.Both the pattern and text should be legible in icons of all the three sizes
Correct
The pattern or text in the icons is illegible.