How can I check if a used car attracts a tax premium?

When buying for example a two year old car is the seller either private or a dealer obliged to inform you that when new it's list price was over 40k and is therefore subject to the extra premium tax until...

Does the premium car tax £40,000 rate include options?

If I purchase a new car sub £40,000 it is not subject to luxury tax but if I add options which take it over 40k is it liable to the luxury car tax?

What happens to premium rate VED once my car is six years old?

I bought and taxed my car in Jan 2024. It was first registered in May 2019, and had a list price above £40k so for 2024 I paid the additonal tax rate. Since the car will be 6 years old in May 2025 can...