Yes, technology advances. We're no longer pedaling around on penny farthings or driving around on Benz Patent-Motorwagens, but the technology is the same basis in many ways, just evolved.

Is fusion weapon research informative of fusion reactor research, and vice versa?

Not even remotely useful. If it was, there would be no more research on fusion reactors. They'd just process the heaps of government data available from both full weapon tests & other research projects.