What's the china fir, is it fir wood?

 no, it is not a kind of fir wood though it called china fir wood, its genus name is Cunninghamia honours, for its details, pls see the blow description in Wiki.

/wiki/Cunninghamia

What's the water-based paint?

it is a kind of very environment paint, just use to stain color on product, we do it by dig

can you custom it for me, such as the size, design and so on?

yes, we can

How long it can used in outdoor environment?

at least fine years with any protect, china fir wood has great ability to keep well in outdoor environment, so pls don't worry.

What's the MOQ, is it 50pcs?