How Do Inventory Picking Rules Works?

I have some questions about the picking rules, specifically regarding the three sorting criteria: lot , sub inventory, and locator.

For the FIFO rule in lot, is the sorting based on the original receipt date or the receipt date?

What does “receipt date asc” mean for sub inventory and locator? Does this mean selecting the sub inventory or locator with the earliest receipt date for picking, or does it mean using the onhand with the earliest receipt date within that sub inventory or locator for picking?

If I specify the sub inventory and locator during the picking, does that mean the sorting of sub inventory and locator no longer applies?