Land Questions

Being a sort of new player,I have a few questions:
1) What is the difference between Classes of SIms , eg Why is a class 5 sim better than a class 4?
2) I understand the original mainland , however there are 3 big land masses ( I'll call these continents) Are these considered islands and are they subject to different land tier fees? or just the small independent islands subject to these island fees.
3) When is the new continent going to be available for land purchases?
appreciate the help.
Sorry if i placed this in the wrong area
Thanks

1) Class 4's are slower than Class 5's

2) There are no differences between the pricing for land on those, at least tier wise. Those are not considered islands, simply new continents.

3) Umm.. depends on when they release new sims.

thanks