How come hallow block been used? Is those holes been covered or initially is Open AIr concept?

correct, but why it beeb use when you extended your kitchen? Not the normal Red or Grey bricks?
This type of brick normally use on Open area concept...

Is brick Hole facing upward and cement been pull into those holes, or only cement the suffice...
I worry it may not able to suitain the load but perhaps Terence should talk to the contractor to get more info. He should able to give advise