Order of doing things assemble then Stain or Stain first

Newbie question, I have partly made a new 4 legged bar stool, with slats for the the seat. I am at the point where I need to assemble it. I would like to stain it a teak colour (it is radiata pine). going from what I have read on here I will, sand the peices, then wet then dry then sand again then apply the stain (thinned black japan).
Two questions.
1. Should I assemble it all before doing the sanding and staining?
2. What finish would I put over the black japan stain, shellac?

Regards
Mike.

Generally, assemble then stain. The exception would be things which you cant really reach after assembly.
If you stain before assembly then any rework, glue spills or sanding/blending will marr the stain.
Dont forget, if staining pine you will likely get a blotchy result unless you use a Pine Sealer first. Feast and Watson make one, available at Bunnings.
Cheers
Arron