What is the main function of the stomach acid?

It starts the digestive process (for certain foods - to satisfy the pedant who also answered) and kills bacteria and other unwanted creatures you have eaten.

To say that Stomach Acid is designed to provide the correct acidity for protease enzymes is to put the situation backwards.  Enzymes as a group of chemicals do not "need" to be in an acid environment to function.  Therefore stomach proteases have been adapted to function in acid that is there for other reasons.

THE STOMACH ACID WHICH IS HCL   PROVIDES AN OPTIMUM PH  FOR THE WORKING OF ENZYME RENIN AND PEPSIN    AND ALSO KILLS GERMS FOUND IN THE FOOD EATEN
   LOVE YOU

Gastric acid is one of the main secretions of the stomach. It consists mainly of hydrochloric acid and acidifies the stomach content to a pH of 1 to 2.

Chloride (Cl?) and hydrogen (H+) ions are secreted separately in the stomach fundus region at the top of the stomach by parietal cells of the gastric mucosa into a secretory network called canaliculi before it enters the stomach lumen.

Gastric acid acts as a barrier against microorganisms to prevent infections and is important for the digestion of food. Its low pH denatures proteins and thereby makes them susceptible to degradation by digestive enzymes such as pepsin. The low pH also activates the enzyme precursor pepsinogen into the active enzyme pepsin by self-cleavage. After leaving the stomach, the hydrochloric acid of the chyme is neutralized in the duodenum by sodium bicarbonate.

The stomach itself is protected from the strong acid by the secretion of a thick, protective mucus layer, and by secretin induced buffering with sodium bicarbonate. Heartburn or peptic ulcers can develop when these mechanisms fail. Drugs of the antihistaminic and proton pump inhibitor classes can inhibit the production of acid in the stomach, and antacids are used to neutralize existing acid.

it does not start the digestive process... that would be the saliva (turns some starches into sugar via amylase)....

stomach acid contains hydrochloric acid and pepsin.  The first helps break down the large lump into a liquid of food and the pepsin breaks the food into its protein counterparts

The stomach releases proteases( protein-digesting enzymes such as pepsin) and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH for the proteases to work

it means that your stomach releases some enzyme ( a kind of a liquid ) to digest proteins ( the protein molecules are quite huge to breakdown, but there are two problems,

1) your food may have tiny bacteria
2) the enzyme works only if there is an acidic nature medium ( a sour medium to say in simpler terms )

this is where your stomach acid ( HCl ) comes to ur rescue.

it kills those bacteria, bcus its an acid.

and it provides an acidic medium so that the enzyme could do its job.