Slur or tie rule for chords in piano

Question

I know there are a lot of questions asking related points but I haven't found an identical question to mine.

Question: Is there a rule for identifying a tie from a slur in piano chords? Do you need to have a curve in each note of the chord that is a tie?

An example:

1. Is the B from the red circle or the D from the blue circle a tie?
2. If the red circle had the same chord repeated (BD and BD) with the same curve as now, would the whole chord be a tie?

Answer 1

You'll notice that ties are drawn much more closely to the note heads. There is no tie in the red circle, but there is in the blue one.

For multiple notes to be tied, for each note tied a separate curve is drawn.