There are six worlds: the world of visible object, of sound, odour, flavour, tangible object, and thinking. They are different from each other, different conditions all conditioning differently. But without the Dhamma we think ‘we’ are experiencing colour, sound , ‘we’ are thinking , we are happy or not. Through understanding Abhidhamma this truth can begin to be seen and so the books align exactly with what is real here and now.
The sense door processes and mind-door processes are always continuing and some people even think that seeing and hearing or thinking happen simultaneously - simply because of the rapidity. But there is always only one world, for a moment and then a new world again and again.
I don’t think so. The object of eye consciousness has to be ittha or anittha. Take an example of an attractive diamond ring that had fallen in some dog faeces . The moments of seeing the attractive colour are different from the moments of seeing the ugly brownish ones. But in a split second billions of processes occur and so this distinction may not be apparent.
This topic has some useful information:
objects