Please note the following correction:

Rnd 6 Ch 4, tr in same beg ch, *tr in next 2 dc, hdc in next 2 dc, sc in next 5 dc, hdc in next 2 dc, tr in next 2 dc, (2 tr, ch 2, 2 tr) in next dc; rep from * 3 times more, then tr in
next 2 dc, dc in next 2 dc, hdc in next 2 dc, dc in next 5 dc, sc in next 5 dc hdc in next 2 dc, dc in next 2
dc, tr in next 2 dc, and in beg st work 2 tr, ch 2, join with slip st to top of beg ch. Fasten off.

Please note the following change to the instructions of the Finishing of the Collar:
Row 1 Hdc in 3rd ch from hook and in each ch to end, sl st in next 2 sts of front and back piece, turn.
Row 2 Hdc in back loops only in every st to end of row, turn.
Row 3 Ch 2, hdc in back loops only in every st, sl st in next 2 sts of front or back piece.
Rep rows 2 and 3 until neckband has been joined to neck opening.
Join the first and last row of neckband tog with sl st.
Fasten off.