She became an humanoid when she Spoiler BECAME A GOD!!!!! So, it's just after the Elf Village Battle (from the Idiot's POV). Chapter 202 is when she awakened to her new form.
Thx ... Last question should i read the extras or just skip it .. Does it affect the story?? Thx in advance
The side-story are a different version of the events that are to come. The side-stories before she became humanoid (the Idiot's story) explains several stuffs about the world that Kumoko didi'nt have the opportunity to know since she was a spider in a dungeon. They also explains some events that are to come and that Kumoko will just brush over since they're not important to her. The side stories that come after she became humanoid (the Blood and Oni's side stories) are fun. They explains several stuffs about what is happening that aren't explain by Kumoko. Plus, the Blood side-story happens around Kumoko. Later, Kumoko will talk about those same events and it is fun to see the two different POVs. So, yeah, read the side-stories. They aren't that essential but thye still help to understand (and the blood's ones (and some of the oni's ones) are fun)