What you need to do is make the texture of the area which you want unscratched to be sticky or metallic because this will stop your cat scratching the furniture.
You can use shelf paper with the sticky end facing outwards therefore if they decide they want to scratch that place they will find their paws momentarily sticking to the paper.
Obviously they do not like this because it restricts the use of their legs and they feel they do not have control of their claws.
To make a sofa or anything metallic you should wrap it in aluminum foil which should deter their claws elsewhere.
You can also prevent your cat scratching the furniture by adding smells onto it as feline hate certain aromas.
They tend to hate citrus, coffee, garlic, menthol, Tabasco sauce, cayenne pepper, ginger and any alcohol based liquids.
The best thing to do here is to spray lemon air freshener because the other fragrances are not ideal for home.
The reason why your little tiger scratches is because it is their form of play and exercise and essentially they need to keep that hunter's instinct.
Also your cat likes scratching the furniture because it is sturdy which the perfect base to sharpen their claws is.
If you buy a post for them to start clawing at you need to make sure it is very sturdy otherwise they simply won't use it.
Finally you need to make sure their post is very tall so that they have to stretch to reach the taller places of the column.