1) It is very likely that non-metal tools persisted for a long time after the advent of iron and bronze.
Flint is actually a pretty good material for arrowheads and other small cutting tools as it can take an extremely sharp cutting edge (indeed obsidian is used even now for specialist surgical tools for eye surgery etc) and unless you are trying to penetrate armour its brittleness is not a major drawback.
Flint also has the advantage that as long as you can get the raw material all you need to make it is skilled labour. Unlike iron smelting you don;t need any sort of industrial infrastructure and knapping tools can be carried in a pocket. Clearly this is a big plus for small communities of semi-nomadic hunter gatherers.
The big advantage of metalworking is that once you have the facilities set up and a ready supply of the raw material you can manufacture tools fairly quickly and in quantity. This means that any sort of metalworking is inherently leaning towards a trade based economy based around a more settled community.
It is also important to bear in in mind that the iron of the iron age is not remotely the same thing as modern steel and primitive wrought iron is in many ways inferior to bronze as a material for tools and the ability to produce steel would have been almost magical and certainly not a technology which would proliferate very quickly.
Equally while the best flit tools are works of great craftsmanship it is also true that you can just smash a flint with a rock and get a load of usable sharp edges.
Having said that wrought iron has some significant advantages in that it is a very versatile material and can be used for nails, wheel rims, cooking pots, buckles agricultural tools etc etc so once a community starts to rely on iron for these more domestic applications it makes economic sense to phase out flint knapping and consolidate toolmaking with the blacksmith.
Iron also has the advantage over bronze that in many areas (eg central Britain and Scandinavia) there were abundant supplies of good quality iron ore near the surface and plenty of forests of fuel to smelt it as well as clay and limestone for smelting as opposed to bronze which even now is very expensive as supplies of copper and especially tin are less abundant and harder to get at.