"doing" or "to do"

[xxwzs]

Two Groups of sentences.
1. Many citizens, young and old, walked and laughed, exotically dressed in themed costumes, ______ Halloween in New York City.
2. Many citizens, young and old, walked and laughed, exotically dressed in themed costumes ______ Halloween in New York City.
A. celebrating B. to celebrate
3. That High Speed Railway opened to traffic last year, ______ the two of those economic zones.
4. That High Speed Railway opened to traffic last year ______ the two of those economic zones.
A. to link B. linking
(There is a difference between the two sentences of each group--comma.)
Could you please help me with these sentences? Which are the right answers?
I’m here waiting for your help. Thanks.

 

[xxwzs]

1. The commas around exotically dressed in themed costumes function as parentheses. We are told simply how the citizens were dressed while they were celebrating Halloween.
2. The citizens were exotically dressed in themed costumes in order to celebrate Halloween.


Can you now see the difference in meaning between #3 and #4?

You have perfectly answered my questions. What you have told me is what I really want.
According to your opinions, the answers given by you to #1 and #2 can not be exchanged with each other, right?

 

[Matthew Wai]

I think they mean differently because 'celebrating' and 'to celebrate' modify 'citizens' and 'dressed' respectively, but I am not a teacher.

 

[Tdol]

#1 and #2 can not be exchanged with each other, right?

Right