Two needle baby sweater advice

hello!
I am new to knitting and just starting on my second baby sweater: the famous zimmerman baby sweater on two needles. I’ve seen others ask this same question, but wasn’t able to locate a response…if someone can offer advice or point me in the right direction i’d really appreciate it!

This is sort of a 2 part question. The directions state that after about 16 rows of garter stitch to switch to the pattern. Then is says “At 4.5”, work 25 sts, then work back-and-forth on the next 28 sts (plus 7 sts cast on at each end of them; 42 sts in all) for about 4" sleeve."

1: what does she mean by ‘work back and forth’ ?
2: how are these directions different if i follow the advice of many bloggers that suggest doing seemless sleeves with circular needles?

thanks!!!

EZ has a lot of sweaters…do you mean The February Sweater? I haven’t made it, but thought having a name might help those who can help you.

Yes, that is the one!

Back and forth means knit flat, not knit in the round.