That's a pretty impressive innings for a Dualis. You obviously maintain it well and drive it sensibly. The engine light on your dashboard is telling you that the car's on-board computer has noticed something isn't right and needs to be fixed or reset. This could be anything from a stretched timing chain to an oxygen sensor in the exhaust system or dozens of things in between.

The best approach is to have the car scanned to see what fault codes the computer throws up. From there, you'll have a much better idea of what the problem is.

The orange or yellow engine light means the car is still safe to drive, but you still need to have it looked at as soon as you can to avoid doing further damage to whatever system is not working properly. If the warning light (of any sort) is red, then you should stop driving as soon as it's safe to pull over and have the vehicle towed to a workshop.

Providing you have used the correct battery and have installed it correctly in the fob there shouldn’t be any problem. Go to a Nissan dealer or an auto locksmith and have them sort it for you

Both are well suited to everyday use around town. They're comfortable, fuel-efficient and safe. The Dualis is a little cheaper than the Sportage, but I would definitely go for the Sportage. I would expect them to have a similar resale value when it comes time to sell, but the reputation of the Sportage for quality and reliability would make it easier to move on.