Will it hold a large cat?

No. The stated maximum load is 10 lbs, so it suits kittens and small-to-average adult cats. A large or heavy cat could pull the shelves off the wall.

Does it come with wall mounting hardware?

The package lists the shelf set and a manual. Check the box contents for anchors and screws, and use fasteners matched to your wall type, such as drywall anchors or stud mounting.

How much floor space does it save?

All the main pieces mount on the wall, so the floor stays clear apart from the space below the lowest perch. That is the main reason to choose it over a floor-standing cat tree.

Is the scratching post replaceable?

The jute post and scratch board are fixed parts of the set, and no replacements are listed. When the jute wears through, the post is the part most likely to need attention.

What tools do I need to install it?

You need a drill, a level and a stud finder or wall anchors. Plan the layout before drilling, since the three tiers, condo and hammock each need their own mounting points.