Material: High-strength aluminum

Yes — see the Fold N' Hold Deluxe Cube (BG-CUBE) if you just need the cube without the line and bags

Are the gaffs on the Buckingham climber set replaceable

or any other object without having to tie a knot

Minimum Tensile Strength: 9

YALE KERNMASTER ROPE 1/2" DIAMETER by-pass Material: High-strength aluminumStatic rapelling Kernmaster line is constructed with a traditional "mantle" sleeve consisting of 48 strands of polyester. The inside, or "kern," is a braided core of energy absorbing nylon. The core is fully steam stabilized to enhance the rope's flexibility and prevent hardening in service; the braid also bends more easily than most ropes. Tensile Strength: 10,500lbs Diameter: 1 2"