1. It needs to be booked in booking class J/C/D/I. For HND-JFK the cost will be 45,000 miles. More details here. https://www.jal.co.jp/jp/en/jalmile/use/jal/upgrade/

2/3. The easiest way to look would be to go to your reservation on JAL's website, scroll all the way down, and look for an Upgrade button on the bottom right. Go through the flow there and you'll see whether there's space available or if you'll be waitlisted for an upgrade seat.