It seems that not all the hidden levels in the score list are full ones. For example, the Aquarosa battle seems to count as one of them, and probably there are other boss battles or short phases that may be at that list too.
Even so, we have seen that there are other levels that completely changes if you access them from a portal of a previous mission like Area 3, that under normal circumstances is a three phase all-range level focused on the walker and the gyrowing, but if you enter it from the portal in Corneria it becomes an on-rails level with Arwing inside the space colony. We haven't seen how it changes, but probably Zoness will get too a similar treatment seeing that if you arrive from Area 3 it's a stealth mission with the Gyrowing, but it you have the Arwing if you enter it from Corneria, probably changing to an action focused mission unlike the original.
About the medals, some of them are scattered throughout the levels, but there are others you can only get by beating a determined score, just like the SF64 ones. Also there seems to be three golden rings with medal ribbons in them, so probably you will get a full one when you catch all of them.
I'm really curious about what levels will get full alternative missions and how them all will change when you arrive them with a different path, but I suspect that at the end the number of full levels will be the same as SF 64 (16).
