Removing metal disc ring from chocolate mousse: which method should I use?
The goal is to melt the outermost little bit and let the ring mold slide off.  Make sure they have had plenty of time to set up before unmolding.

The torch will work, although I would use a towel soaked in very very hot water, then squeezed dryish&mdash;just wrap it around the mold for ten or twenty seconds.   This maybe gentler than the torch, and less likely to go too far.

Edit: 

Agar agar us not freeze stable, so you should not freeze your confections.

I imagine that eight hours is sufficiently long for a good chill, but I would go overnight if you can--a lot of labor goes into this sort of dish, so you don't want to loose the work.