I'm completely new to Apple computing. I have had iphones over the years but wanting help on the laptops.

I have been looking at the

Apple Macbook Air Core i5 4GB 256GB SSD 11.6 inch Mac OS X Yosemite Laptop

Does anyone have this laptop that they can give there opinion on? Any pros or cons?

Wanting to know how old the 4th generation of the macbook air is?

Also can this be updated from OS X Mavericks to OS X Yosmite with 4th generation?

Thank you