Armhole edge = odd rows
Neck edge = even rows
No they're edges and there's an edge on both the odd and even rows.
Starting with row 5 do not
do a dec on the armhole edge, only the neck edge. If you continue to dec on the armhole it will look like the V neck and after 4 rows of decs it should be straight up - look at the picture. The neck decs will also only be every other row, and you have them on every row.
Lets try it another way -
1, rs - dec, work across
2, ws - work across, dec at end
3, rs - dec at beg, work across, dec, cable sts
4, ws - cable sts, purl, dec at end of row
5, rs - knit across, dec, cable sts,
6, ws - cable sts, purl
Repeat rows 5 and 6 until you have 36 sts. Then only dec at the neck edge every 4th
row on the RS.
If you could link to the pattern, that would help us make sure you're interpreting it correctly.