Interpretation of the word "immediately" in Phase 3 or Phase 4
I can't see any reason why Trade Master would circumvent the normal rules for playing an Action.  I think all that the "immediately" implies is that, when you play the card during phase 2, you get the resources straightaway at that point.  

Why this particular card would use the word "immediately" when all action cards are specified by the rules as taking "immediate effect" isn't very clear - but in situations like this I usually assume a slightly loose translation from the original German, rather than reading a special meaning in.  Perhaps a native speaker could tell us what the wording on the German cards are?