Flush Woes

I am completely new to this game and trying to teach it to a friend (also brand new to the game,) who has a tendency to argue everything and tie things in knots. At least I know what question I need to ask all of you:

Can you count a flush during "pegging" (I did use that term correctly, yes, no? When you are playing alternately?) And if so, how many of the same cards do you need to have for it to count as a flush? And, correct me if I am wrong ... you must have 4 of the same suit to count flush in your hand (five if it's the crib hand.)

Flushes

Flushes are never scored while pegging. They are only scored in your hands after pegging. You must have all 4 cards in your hand (with or without the starter card of the same suit) to score 4 or 5 points, and you MUST have all 5 cards in a crib (hand + starter card) for a flush in the crib. A crib flush is very rare and only seen once every 700 cribs.

Flush while pegging.

Someone please answer the question. Can you score a flush while pegging?

Flushes while pegging

No Never