Which organism's filaments are used in the production of Single Cell Protein $(SCP)$?

Statement $P$: Heterotrophic mushrooms are cultivated globally.
Statement $Q$: $A$ cow weighing $250 \, kg$ produces $200 \, g$ of protein per day.

Single Cell Protein $(SCP)$ as a food source provides which of the following nutrients?

Consider the following four statements $(1-4)$ and select the option that includes all the correct statements:
$(1)$ The unicellular $Spirulina$ can produce large quantities of food rich in protein,minerals,vitamins,etc.
$(2)$ $Methylophilus$ $methylotrophus$,because of its high rate of biomass production and growth,can produce $25$ tonnes of protein per day.
$(3)$ Common button mushrooms are rich in Vitamin $C$.
$(4)$ Rice varieties have been developed which are rich in calcium.

Which of the following statements is incorrect regarding the use of Single Cell Protein $(SCP)$?

The alga rich in protein is