I see no reason why the powder chemicals shouldn't be OK provided the packets are still sealed. As for the liquid print and film developer all you could do is try them. Use, say, a 4x5 piece of printing paper for a negative and see what you get. For film, try developing a film leader in room/daylight for the time specified by the developer for that film, then fix and rinse. The leader should turn black. Hold it up against a clear incandescent lamp filament such as a clear 75/100W bulb. If the leader turns the filament into a white/orange coloured wire then the developer would appear to have done its job. Try a few negs from an exposed film that you can afford to lose, just in case.
Part of the fun with old chems is trying them out. If you cannot afford any failure at all, dump them.
pentaxuser