The third function "new cells come from existing cells" does not fit the first component of the cell theory described above.
The classical cell theory was proposed by Theodor Schwann in 1839. There are three parts to this theory. The first part states that all organisms are made of cells. The second part states that cells are the basic units of life. These parts were based on a conclusion made by Schwann and Matthias Schleiden in 1838, after comparing their observations of plant and animal cells.
The theory didn't explain how new cells were formed which was later described by Rudolf Virchow in 1858, which states in the third part, that cells come from pre-existing cells that have multiplied.