Monopoly Deal - Suppose, I have 6 cards before I got my turn. I picked up 2 Cards from the deck. Now, I have 8 cards. Can I not use any of the cards in this turn and pass my turn? Which means I have 1 excess of 7 (so i will put 1 card back to the deck). Is this a valid move?
Yes. This is explicitly allowed by the rules:
On your turn:
Play up to 3 cards ... You don’t have to play any cards if you don’t want to.
Drawing an excess number of cards is a legitimate tactic.
Suppose you have 6 cards at the start of your turn, 3 of which are "Pass Go" (i.e., play to discard pile, draw 2 new cards). In theory, you could finish your turn with 11 cards (6 + 2 drawn at turn start, + 3 for each Pass Go played), so you need to discard 4 of them to get back down to 7. You could discard property cards your opponent is seeking, denying them the chance to draw them / steal them, whilst freeing your own hand up.