Also, there were silly questions like if I use the car for social purposes only. I normally use it for social purposes, as I take the train for work. But let's suppose one day there is a train strike and I have to take the car for work. Then let's suppose that day I have an accident... so what happens? Does that mean the insurance doesn't cover?

Broadly speaking there's the following classes of use:

Social Domestic & Pleasure - Normal day to day driving. Shopping, visiting friends or family and pleasure driving such as going to the park or on holiday

Commuting - Driving to and from one place of work in a day. Some insurers include driving your car to the train station and leaving it there while you go to work as commuting.

Business use - Using your car as part of your job, or driving to multiple places of work in one day. There's further sub-divisions of Business use for when you're carrying goods or passengers.

The exact type of journeys covered by the different classes can vary from insurer to insurer with some combining the SDP and commuting aspects. If your insurer differentiates between the two then SDP-only cover would not include driving to work, even one-off occurrences. This doesn't invalidate your insurance in general - just for the times you were using it outside of the covered purposes.

This last aspect is one of the places where the black-box potentially comes in - say some less-than-honest person tried to save a few quid by ticking the SDP-only option but commutes anyway. They then have an accident whilst on the commute, the insurance company looks at the usage data and determines that they were making regular journeys at the start and end of the day, Monday-Friday and it was one such journey they had the accident. A little light digging later and voila the insurer finds out they were exceeding the coverage and they're on the hook for the cost of the claim, and potentially a nice IN10 conviction for driving whilst uninsured. Ouch.

However, I cannot remember very well when was my last claim and the previous insurance company (which was abroad) doesn't have that information anymore. I believe my last claim was about 20 years ago, so when subscribing the new insurance I claimed my last claim was 20+ years ago. What happens if in reality it was 19 years ago? Unfortunately, I have no way to verify that. Does that mean in case of an accident, the insurance wouldn't cover?

You're fine - firstly an accident that far back is unlikely to qualify as a material fact, i.e. something that affects either the price of the policy or the decision to insure you at all, and even if it did they would have to show that you deliberately misled them as to that fact for it to have major consequences Otherwise the most likely scenario is be required to pay the difference in premium. In twenty years of insuring cars in the UK I don't think I've ever been asked about accident history going back further than 5 years and most insurers will only retain the records for 7-10 years in any event.

Also, there were silly questions like if I use the car for social purposes only. I normally use it for social purposes, as I take the train for work. But let's suppose one day there is a train strike and I have to take the car for work. Then let's suppose that day I have an accident... so what happens? Does that mean the insurance doesn't cover?

Broadly speaking there's the following classes of use:

Social Domestic & Pleasure - Normal day to day driving. Shopping, visiting friends or family and pleasure driving such as going to the park or on holiday

Commuting - Driving to and from one place of work in a day. Some insurers include driving your car to the train station and leaving it there while you go to work as commuting.

Business use - Using your car as part of your job, or driving to multiple places of work in one day. There's further sub-divisions of Business use for when you're carrying goods or passengers.

The exact type of journeys covered by the different classes can vary from insurer to insurer with some combining the SDP and commuting aspects. If your insurer differentiates between the two then SDP-only cover would not include driving to work, even one-off occurrences. This doesn't invalidate your insurance in general - just for the times you were using it outside of the covered purposes.

This last aspect is one of the places where the black-box potentially comes in - say some less-than-honest person tried to save a few quid by ticking the SDP-only option but commutes anyway. They then have an accident whilst on the commute, the insurance company looks at the usage data and determines that they were making regular journeys at the start and end of the day, Monday-Friday and it was one such journey they had the accident. A little light digging later and voila the insurer finds out they were exceeding the coverage and they're on the hook for the cost of the claim - Ouch.

It's worth noting here that you likely aren't uninsured in a criminal sense - the insurer will still be considered the insurer of record for purposes of the Road Traffic Act and will have to pay out any third party liabilities. They can decline any first party liabilities however - and may pursue you civilly to recoup the costs they've paid out to the third party.

However, I cannot remember very well when was my last claim and the previous insurance company (which was abroad) doesn't have that information anymore. I believe my last claim was about 20 years ago, so when subscribing the new insurance I claimed my last claim was 20+ years ago. What happens if in reality it was 19 years ago? Unfortunately, I have no way to verify that. Does that mean in case of an accident, the insurance wouldn't cover?

You're fine - firstly an accident that far back is unlikely to qualify as a material fact, i.e. something that affects either the price of the policy or the decision to insure you at all, and even if it did they would have to show that you deliberately misled them as to that fact for it to have major consequences Otherwise the most likely scenario is be required to pay the difference in premium. In twenty years of insuring cars in the UK I don't think I've ever been asked about accident history going back further than 5 years and most insurers will only retain the records for 7-10 years in any event.