i want to know should i build the riser prior to staining/glassing?
It will be much easier to glass if you put the riser on after glassing.
i understand the riser can be built with wood glue.....i want to stain it same color as boat.
I used wood glue but I also completely glass mine, they get a bit of pressure, you could fall on it.
also want to know if external bow/stern stems can be done with wood glue....and if should do before or after glassing the hull. (stems will not be stained)
It is fine to attach them with wood glue but definitely put them under the glass, I guess you could put them on on top of the glass and then glass them but it would be harder to fair them to the hull. They need to be under glass, they take a beating.

am building in an unheated garage...

only need 50 degrees to work with wood glue....this weekend makes epoxy work look pretty far off.

any advice on order of activities with respect to the riser and stems would be appreciated and other items that can be built while waiting for epoxy-curable temps
My advice: patience.

ric