This is something for your council office, since NYLT requirements vary from council to council. There should be a coordinator who could answer all the questions you have. That being said your unit leader probably knows what the customs are in your council. My council does not require ILST or ILSC. I went to NYLT in 2009, it's still one of my fondest memories of Scouts. I had no prior training before I went, I was 15 years old, and Assistant Senior Patrol leader. In my council most of the youth that go are between 13-16 years of age.