Question about Brooklyntweed's Helmock ring pattern

Greetings. I am new member and am having trouble understanding parts of the helmlock ring chart that was made famous by Brooklyn Tweed.
Can someone please explain what zero means? Is this a yarn over:

3rd rnd: (O, k 1) 8 times.

What does “thread over twice” mean?:
13th rnd: * K 2 tog, thread over twice, sl 1 st as if to k, k 1, p.s.s.o. Repeat from * around.

I guess “allow 1st O to slip off left-hand needle” means to drop a yarnover but why would you do this?:

14th rnd: K 1, allow 1st O to slip off left-hand needle, work 9 sts in next O – to work 9 sts in 1, (k 1, p 1) 4 times; k 1,-- * k 2, drop 1 O, work 9 sts in next O. Repeat from * around, ending with k 1 (88 sts).

Finally is there a chart that begins with row 1? I have seen some that begin at later rows, but if there was a chart that began with row 1 that would be great.

Yes, the O is a yarn over. I think these are kind of vintage directions for this doily. I have one version of the pattern in front of me and based on what it says in the next row (after it had you do the thread over twice) it refers to each of the loops as an O. The ‘thread over twice’ must be a double yarn over. The reason you would drop one of the yarn overs off would be to make a bigger than normal yarn over hole in the lace.

I don’t know about the chart.