VEVOR Outdoor Stair Railing Kit, 5 FT Handrails 0-5 Steps, Adjustable Angle White Aluminum Stair Hand Rail for The Elderly, Handrails for Outdoor Steps

I need a handrail for steps between a "stoop" on either side of them. The stoop where the handrail must be installed is level. The bottom post must be cut shorter for this to work. Can the top of the post be cut and the adjustable bracket be reinstalled, or is the top post bracket permanently attached

Are the posts also aluminum? This will be in constant contact with water.

What size drill bit is needed to pre-drill holes into concrete for installation?