I’m no authority on this, but I remember hearing (from a reliable source) that a person has two basherts, and it doesn’t make a difference which one the person marries. I would imagine the name called out forty days before birth is the person they end up marrying.
In regard to the second question, (and this is just my feeling, no source,) I remember on more than one occasion people have told me that so-and-so is dating someone and it was at a serious stage, and to daven that it work out. I never understood that, because just because it got to that stage, didn’t automatically make it right. You want to marry your bashert, and you would like for your bashert to have certain qualities. Does a person really want to marry someone who looks good (as far as shidduchim) if that isn’t really their bashert? Safest bet, daven that Hashem send your (or whoever it is you’re asking about) bashert and that s/he be a good spouse.
Hatzlacha!