In UNO, is it legal to throw a Draw 4 card that you just picked up on purpose?

Question

1. A player decides to draw from the draw pile instead of playing one of his cards (he has a color matching card).
2. He draws a Wild Draw 4 card and he plays it.

Can the next player challenge him because the play is illegal?

According to official rules

NOTE: if you suspect that a Wild Draw 4 card has been played on you illegally (i.e. the player has a matching card), then you may challenge that player. The challenged player must show you their hand. If guilty, the challenged player must draw the 4 cards instead of you. [...]

Answer 1

Yes, the play is illegal. It doesn't matter that the card was just drawn; it is still prohibited.