Alternate rows are every other rows. Think of it as saying 'dec second row from now and then every other row 11 times more. This gets you back to the right side so you can do the neck decreases at the end.
When they say to pattern to the last 3 stitches, that usually means that you're going to continue doing whatever you have been --including any decreases at the beginning of the rows, and as you continue them, you're also decreasing at the front edge.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry