"Ermine" can be regular tort chin or a torted agouti sable. Agouti sable are often called sable chin or light chin. It adds a slight complication to calculating colors when you don't know if you have the chin gene or the sable gene in an ermine. If you have experience with the myriad of shading that occurs when the nonextension/tort is applied you can tell as they mature a bit but it's often hard in pictures or with young kits. That's why I started calling my tort chin versions ermine and my sable versions frosty to keep track of what I was crossing but most use one word or the other for both. I had 1 chin in my starting group that occasionally resulted in the chin versions instead of the sable version of those near white shadeds.
For breeding them you have the combination of what is under the lightened coat and then the nonextension/tort is a recessive that requires both parents to display. If you have a torted regular chin bred to a sable you get the same possible result of any chin x sable. If the sable parent is not carrying the nonextension/tort gene the first generation will not show it and only when breeding them together or to another color that uses nonextension (torts, reds, etc...) will you get more of the ermines. Same for every other color that does not have tort/nonextension. You essentially have a chin crossed to that color for your first generation of offspring.
If you have a torted sable chin instead of torted regular chin then they lack the chin gene but have agouti in place of self. In that case you are breeding sable rather than chin to the other colors even if an agouti sable is more often referred to as a variation of chin you can never get regular chin out of them while you can get sable. When bred to shaded or carriers of shaded you get more sable chin and possibly sables if the torted sable chin carries self. Along with the usual chance of himi or rew that happens when crossing sables or rabbits with shaded background. All of those offspring will again carry the nonextension/tort gene to make more ermines if bred together but not if bred to rabbits that don't have it. You just can't ever be sure when the tort gene is gone or not since it can happen to pass through several generations unnoticed before being crossed to another rabbit carrying nonextension/tort.
Throwing sable point in there gets a little more random because you are no longer breeding out the tort. You can't just ignore the lightened coat when determining offspring if the rabbit carries or already shows another torted color. A sable point displays the nonextension/tort gene. It is a shaded tort. It doesn't come out looking like an ermine because it is not agouti as well. Sable points could result from crosses to ermines if they are sable instead of chin based ermines and crossing sable point or those with sable point background to an ermine of either chin or sable version will get you more ermines. Similarly crossing a tort to ermine of course keeps the tort gene but will lose the shading instead. Combined with the agouti in ermine you will get red/orange (red or orange depending on breed color naming is the same gene as tort on an agouti), possibly torts if the ermine carries self, or possibly more ermine if the tort parent carries chin, sable, himi, or rew. Maybe even sable point but that starts to depend on a lot of recessive (not visible) genes lining up from the background of both parents.
Otter becomes irrelevant as soon as you are only dealing with the self offspring of them. Otter can hide beneath agouti such as chestnut or red/orange but it shows up before self colors. Sable, tort, and basic selfs of black, blue, etc.... did not get the otter gene and you will never see it again unless bred to an otter, marten, or agouti color carrying it.
