The way it works is that we observe how things behave today and make predictions about what we might expect to see if they behaved the same way in the past. We then look at things of well known historical age (e.g. trees up to 5,000 years old) and check if our predictions are reliable. If so, we make predictions of what we'd expect to see for something much older, and then select something we think is around that age and see if our predictions hold good. By cross-checking with a number of different dating indicators, e.g. tree rings, radioactive isotope decay (various), stratigraphic, thermoluminescence, electron spin resonance, optically stimulated luminescence, archeo-magnetic, corrosion, obsidian hydration, amino acids, rehydroxylation, etc., we can estimate the precision and range of each dating method, and use the temporal range overlap to date things within a well-defined range of error.
If the forces and laws were significantly different in the past (within the range of our dating methods), we would not see the consistency between our predictions and our observations that we do.
God formed it but it wasn't formed?
As explained above, we have a lot more than isotopes, and many ways to cross-check dating methods - all based on and dependent on observation rather than belief without evidence (faith) or belief in the supernatural. So no, it's not religion.
Earth is older than what? if you mean that really old bits of Earth might have been blasted into space and then returned back to the surface to fool our dating systems, events like that have actually happened - we have found ancient material (rock) from Earth and from the moon and Mars - but we know about it because it's found out of context, e.g. near or on the surface among much younger material. Crustal recycling due to plate tectonics limits how far back we can date rocks we find to around 4.4 billion years.
No, not really. It's all based on observation and many scientists competing over many years to find the best model to fit those observations - then cross-checking them in as many ways as they can. Each new piece of evidence is checked and, if necessary, the models are adjusted. As I said before, the further back you go, the wider the error bars, so the more likely a new piece of evidence will adjust the models for that era, but the error bars are reducing.
I'm not sure what you're talking about here - dark matter? 'dark matter' says we don't know what it is yet, but it behaves as if it has mass and hardly interacts. It's probably a bunch of particles, but it could be gravity behaving unexpectedly at cosmological distances. Yes, there's a large hole in our knowledge, one of many holes - but that's why we do science; if there were no more holes, if we knew everything, science would be at an end.
Only a really tiny percentage of things that die become fossils, so the vast majority of men and beasts throughout history will have returned to 'dust' without becoming fossils.
Perhaps you could spread that word among your fellow believers