This is the house. I lived in the house. 1. This is the house. I lived in which. 2. This is the house. Which I lived in. 3. This is the house which I lived in. 4. This is the house in which I lived. This is understandable to me.-- Well, I don't. #1 and #2 are not English. #3 would naturally use 'that' or more usually no conjunction: 'This is the house (that) I lived in'.
Well, all I can suggest is that you abandon steps 1 and 2, which are confusing and misleading, since they are not real, and stick with steps 3 and 4, which are all you need.
This is the house. I lived in this house.
3. This is the house which I lived in. 4. This is the house in which I lived.