I have a question about the recipe "Honey Challah" from erinmcdowell. can I use Rapid Rise highly active yeast instead of instant dry yeast
Yes, you can. Even a highly active yeast needs more than instant dry. I'd suggest 1.5 time more.
Interesting discussion of the difference here: http://www.thekitchn.com... I suspect that as long as you are going through the same proofing routine (2 rises) you should be fine. You may want to keep an eye on it though to prevent it from over-proofing. The time actually required may be different. :o)