Advise on Toyota Noah

Dealers would mostly only sell standard size pistons and the only way to get oversized pistons would be to get the help of other parts outlets.

Engines nowadays seldom have wear to the block, unless oil change are seldom done or engine is subjected to abuse.

The most common cause of oil consumption would be worn/bad valve seals and replacing them should reduce oil consumption by at least 70%.

Without taking the pistons out and measuring the wear of the cylinders, it is not possible to know if reboring is required.

Most likely you would only need new valve seals and piston rings.

Nope, diesel engines are a different matter.

The bore would mostly be worn and what you need to do is to replace the cylinder liners if it is bad, which most likely is, as they are subjected to high compression pressures during operation.

Pistons would be back to standard. You would need the machine shop to help you on replacement of the liners.

Usually liners can be purchased from parts outlets. Dealers seldom have them as they are most likely not listed in the parts catalogue.

Yes, block has to be removed and sent to machine shops for them to take the old liner out and press in the new liners after which they would have to hone them to fit the new pistons.