What are these lines on the fuselage of a 747?
No, they are just the boundaries between skin panels. See below for a picture of the 747-8 fuselage during assembly.

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Boeing 747-8 front from side (picture source)

And this is how the panels for the cylindrical section look like before they are joined:



Boeing 747-8 fuselage panels. The original picture (source) is named "wing panel skins", but these are really fuselage parts.