4. What does the following error means: Please select a transaction date that comes after the date you started tracking the quantity on hand of these inventory items?
While cteating a new inventory item the user specifies the Inventory Start Date. All transactions that include this item should be dated after the specified Inventory Start Date. To fix the error specified you need to change the date of the transaction.
5. Where can I see history for a certain item?
The easiest way to see Item history is to find item in the Item List (Inventory → Item List) and in the Actions columns select Transactions. It shows Inventory Transactions by Item report for the selected item for the current month. You may change the filter option to show only specific types of transactions and update the data filter.
Inventory Transactions by Item report is available in Reports → Inventory Transactions by Item.
6. Can I see my total inventory cost / total value of my inventory?
It is shown in Reports → Inventory Total Value. Please be aware that The value of the items is calculated based on the purchase cost that is specified in the Edit Item page.