The earth changes its magentic polarity every few thousand years or so.
The hypothesized reason is due to internal convection changing the dynamo. Note that earth's core is largely iron and nickel.
Since your planet has a much larger proportion of iron in the core and a much larrger radius, it can be assumed to fluctuate its magnetic polarity much sooner as the opportunity for convection currents will be more, and as iron is more magnetic than nickel (.https://physics.stackexchange.com/questions/318215/nickel-iron-and-cobalt-attraction-strength-to-a-magnet).
How soon will depend on the exact composition, so you can set this as per your convenience. But since this is still a geological phenomenon, and magma has a very high density, so the change in magnetic polarity should not be very frequent. I would suggest to pick a value in the range of 100-200 years.
It also suffices to say that due to large presence of iron, many a surface rock will turn out to be magnetic, with varying strength at different areas.
Given this increased magentism, any solar flare is bound to produce much stronger reaction, which will also be amplified by the short distance between the planet and sun.
So, you can expect
Technology for infrastructure etc to be complicated. For example, simple digging etc will take more time as the tools will keep getting magentised more frequently
Magentic interference to vary and make electric transmission difficult/ unreliable at times.
Much more outages of electricity grid due to solar flares
Which will lead to less reliance on technology that we see today due to frequent blackouts
That said, technology is not just for electronic products, but also for biotech, energy, space, nanotech etc, which should not have that profound an impact due to increased iron.