A social for an engaged couple or already married couple? If it's an engaged couple (such as an engagement party), I'd bring something small, like a bottle of wine and a congratulations card. If it's an already married couple, I would bring a gift if I did not bring one to the wedding (it's okay to send gifts up to one year after the fact). But, if we're talking about just some kind of get together, I'd do a very small host/hostess gift (flowers, stationary, kitchen utensil, etc...)
No, the gifts are given as a boost to the new couple. You are not obligated by any means to provide a gift to a married couple that is renewing their vows.
* Yes, if a married couple are renewing their vows then a gift should be given unless the invitation has stated that no gifts be given.
No, dates do not have to give a gift to the wedding couple. Your date does.
If you were invited to the wedding and can't make it because of traveling plans then yes, when you get back you should send the couple a wedding gift.
I think a couple weeks before would be find.
Decanters are great wedding gifts if the couple drink.
The correct way to address a gift is "Mr. & Mrs. James Smith". The couple is already married so it is proper to address it this way.
I don't think you should if you weren't invited to the wedding. In polite society, gifts are NOT to be expected. If you want to send a gift it is up to you whether you get an invitation or not.
No they just give them a big wedding gift
Once a gift is given at the wedding then these gifts of owned by the couple and if they divorce it will be up to them to decide who keeps what.
Yes, but include a gift receipt in case they need to return it.
There are no traditional gifts for a 29th wedding anniversary. The modern gift for a 29th wedding anniversary is new furniture. You can give a couple a gift for their home or something that you know they will like for their anniversary if you do not want to use the modern gift idea.