Sourdough and Starters

Help improving my loaf

My bread seems undercooked and dense on the inside and I dont know why.

Trouble with Crackes

why is my dough so stiff?

Commercial Yeast in Sourdough?

My second loaf

Starter doubling in 5 hours but dough doesn't follow. What gives?

Sourdough loaf without a starter

Someone uncovered my starter

Threw out my starter by accident, how should I use my current pizza dough to recreate it?