The batch code of the product can be found on the exterior of the product box as well as on the product itself.
For bottled products, it is often printed on the underside of the bottle, just below the label, and sometimes even on the label itself. Note that a printed batch code on the label is not an indicator of a counterfeit product (despite what some online sources say).
For tubular products, the batch code can be found on the crimp of the tube (the top most part of the tube when placed upright).
The expiry date of a product only holds if the product is unopened and unused. Once the product is opened, the product is only good until the PAO or the expiry date, whichever comes first.