1) No, some are rooted by cuttings and grow on their own roots. Some are grown from seed, but trees grown from seed are not true the variety they arose from. To maintain the purity and characterisits of a variety or cultivar the plant must be propagated by grafting or cuttings.

2) Hard to say.

3)The only con to the maple on its own roots is that it will be slower to establish than the grafted plant. Maples grown from seed have good vigor, but when you compare rooting a cutting to grafting a plant, the rooting process of the cutting will take quite a bit longer to achieve the same canopy size of the grafted plant and without proper knowledge and the appropriate process, failure is quite common with rooted cuttings.

1. not all japanese maples are grafted, there are tissue cultures, there cuttings, and my favorite tissue cultures.

2. because of it's red lacey-ness, might be a 'dissectum' and depending if you prop it up with a stick it might grow as tall as you want, otherwise it might be as small as a foot.

3. con: when it matures there's a disproportion to the size of the graft and the graftee.