Alternate name of $TCA$ cycle is

What is the net gain in a Krebs cycle?

How many $ATP$ molecules are produced directly in one $Krebs$ cycle per acetyl-$CoA$ molecule?

Where does the $Krebs$ cycle take place?

The enzymes of the $TCA$ cycle are located in the mitochondrial matrix,except for one which is located in the inner mitochondrial membrane in eukaryotes and in the cytosol in prokaryotes. This enzyme is:

Identify $A$ and $B$ in the given reaction:
$\text{Pyruvic acid} + \text{CoA} + \text{NAD}^+ \xrightarrow{\text{Mg}^{2+}} A + B + \text{NADH} + \text{H}^+$