What is the product formed when acetaldehyde reacts with $PCl_5$?

The major product of the following reaction is

The given reaction is an example of an intramolecular aldol condensation. Identify the product $(A)$ formed in the reaction:
$1,5-\text{cyclooctanedione} \xrightarrow{H_2SO_4, H_2O} (A)$

Identify product $(A)$ in the following reaction:

Which of the following compounds undergoes the Cannizzaro reaction?

$CH_3CHO$ and $C_6H_5CH_2CHO$ can be distinguished chemically by