Both Green and Blue finishes (as per definition Finish) at position 1. There is no current.
 

ISAF Case 127 states that a boat clears the finishing line and marks when no part of her hull, crew or equipment is on the line, and no mark is influencing her choice of course.
 

Does Blue clear the finishing line at position 2 and therefore stop racing before position 3?
 

Yes.
 

Does Green clear the finishing line at position 2 and therefore stop racing before position 3?
 

At position 2, Green has cleared the finishing line. If the boat had adequate speed to overcome the mark, the finishing mark was not influencing her course at position 2. Therefore she had cleared the mark at position 2, and so was no longer racing when she then touched it. However, see A3.
 

Would the presence of current along the finishing line change the answers to questions 1 and 2 above?
 

Green would still be racing at positions 2 and 3 if conditions, including a strong current and wind strength and direction, made touching the mark inevitable.