These can be used top and bottom.
They are 44 inch long and 1/2" square.
No, you need to drill the holes. Drill an appropriate size hole for your balusters top and bottom. Drill 1 inch to 1.5 inch deep up into the handrail. Drill 1/4 inch to 1/2 inch into the tread / floor.
I'm sorry but our balusters will not work for that purpose.
Yes. We cut them with a saw
Check your building code. They need to be a maximum of 4" gaps in our area.