Hafrashat Challah

What amount of flour requires that hafrashat challah be done?

2.5 lbs take without a bracha. 5 lbs make a bracha

What do I do if I made 2.5 lbs and forgot to take challah?

Where is the dough now? Baked? Take Challah from the baked goods.

We usually prepare 5 lbs of dough but bake only part of it for this week’s Shabbos Challahs. The rest is stored in the freezer for the next Shabbos or two.
Can we separate Challah from the 5 lbs of dough with a brocha?