Anaerobic respiration was first demonstrated by whom?

Identify the products marked by $(i)$ and $(ii)$ in the following pathway:
$3$-phosphoglyceric acid $\rightarrow$ $(i)$ $\rightarrow$ Pyruvate $\rightarrow$ $(ii)$ (with $NADH + H^+$ being converted to $NAD^+$)

In mature mammalian erythrocytes,the respiration is

What is the net number of $ATP$ molecules produced during lactic acid fermentation?

During anaerobic respiration in yeast,what are the end-products?

Fermentation is performed by: