I have a couple of questions regarding the Form of Beast spell.
Is a sorcerer who learns this spell limited to one beast? Can the sorcerer change the beast from scene to scene, or have another way to learn forms?
The spell description says the form is mostly cosmetic. But with spending momentum, a sorcerer can add effects (increase attribute, for example). It is clear that the wolf example includes these momentum expenditures. Is it required of the sorcerer to take the form of wolf with these momentum spends? Can the sorcerer choose to cast form of the beast, choose a wolf and only expend one momentum for one of the two effects (Nature’s Brawn)? Can the sorcerer change this up in a later scene and use How Sharp These Senses?
The spell isn’t limited to one beast unless the GM decides to create a limitation like that. I wouldn’t limit it that way but for flavor purposes it could be interesting. As far as the momentum spends for added effects you have to have the spell in effect to use it so it would stand to reason that you would have to have taken the related shape. Again this is up to the GM. And changing the effect to another would require a new momentum spend. (All of this is my opinion of course.)
Form of a beast. - learning new forms isn’t a standard thing at all. If a GM wants to allow it they might look to experimentation (Skelos page 65) or simply charge a 200xp talent for each additional form.
When shifting forms the discount applies to one animal shape. When transformed the character gains all the benefits they pay for with Difficulty/Momentum and shifting these requires a new spell. Its entirely up to the GM if they wish to be liberal with the creatures capabilities but GMs can be strict and require extra momentum for different abilities. (momentum spends are the GMs to control)