My S4 mini got the Play Protect update. And it is definitely old enough that I wouldn't expect it to still get updates. NB I now have a S8+ So no problems receiving updates.
As for the CGA I want sellers to simply state how long they intend to provide spare parts and service support for the items they sell. In my day job, when customers ask me to recommend them brands of plumbing fittings or gas appliances. I always only recommend the brands that have good spare parts support.
Partly to provide better service to the customer and partly to reduce the risk that a customer might make a CGA claim against me due to spare parts not being available.