can u charge the iphone 12 with a normal lightning charger?

Yes and no. It will be faster than a 5 watt charger, but not as fast as a USB-C charger and the USB-C cable the phone comes with.

The difference is it will charge at a 12 watt rate with a USB A cable and a 12 watt or greater USB-A charger, but at a 20 watt rate with a USB C cable and USB-C charger.

If you charge overnight, every night, as you should, the speed of charge doesn’t matter. The phone will be fully charged in the morning, and will last the day, unless you are a very heavy user of video or interactive gaming apps for hours at a time.

Yes. It will not fast charge, but it will be able to fully charge the phone.