Im very confused why my duplicate chair object become black and white and cant collide after i duplicate in Blender. but original chair not error. What error is this?

looks like you have multiple questions in a few words.

1: duplicated object becomes b&w.
dunno why you duplicate in blender as you can do it by code.
the b&w is simply that the default texture is applied, but because your obj doesn’t have uvs, default ones necessary for texture material are applied to prevent crash. So obviously as you do not export with uvs, the way you “duplicate” misses something somewhere.

2: can’t collide. You mean you define a collider using physics??
If you change the transform or object center. and especially if you export as obj, which is a format that burns transforms into vertices (it doesn’t support transforms or scenegraph), your collider works, but is located else where.