Lesh18, on 2012-April-25, 12:23, said:
Yes, the opponents are entitled to exactly the same information as you have. You should provide this if they ask you about one of your partner's bids. You should also expect this from opponents when you ask them about their calls. Some opponents are less forthcoming than others - if you find out that an opponent's explanation was less than complete and think this might have affected the outcome then you should speak to the Director about it (if one is present).
Lesh18, on 2012-April-25, 13:56, said:
Does the vulnurability - non-vulnurability really play in important role in bridge game? Or can it be avoided for the same experience from the game?
Yes, the vulnerability makes some considerable difference in certain situations. If you are just playing practise hands with friends then I would suggest playing one hand with both pairs not vulnerable, then the second and third hands with the dealing side not vulnerable and the non-dealing side vulnerable, and the fourth hand with both sides vulnerable. I personally use a pair of jokers on a corner of the table to indicate vulnerability which seems to work quite well (no joker = both nv, one joker = pair with short side are vul, both jokers crossed = both vul).