Yes, you can enable the inventory option for a product and enter the available stock. Neartail automatically keeps track of the product orders and updates the available stock. When the stock becomes zero, the product is marked as sold out. Users will not be able to place orders for sold out products. Please note that the inventory feature will not work for products sold by quantity or weight with + - spinner widget. For detailed instructions, refer to the help article below. Enable inventory https://neartail.com/order-form/add-products-with-limited-stock.html

but why i cannot see the gear icon next to the product in the edit mode of the form?

If you are using the new editor, then you will have to click on a product to select it and then click on the gear icon for that selected product. If you are using the WYSWIYG editor (old editor), you can directly click on the gear icon next to the product to open the product settings page.