Quick and easy question: Does the 3-Action Level 1 Heal Spell heal for 1d8, or 1d8+8? Is it a general rule that a 3-Action variant of a spell includes the effect of the 2-Action variant? Or is it a general rule that it does not?
The three-action unheightened Heal spell heals 1d8. The three casting options are mutually exclusive options which do not interact with each other.
The spell says, "The number of actions you spend when casting this spell determines ...". If you spend 3 actions, you use the properties from the 3-action entry.
I don't have a hard proof, but inheriting properties from the lower-action versions creates a lot of contradictions. For example, if you used the system to cast a 3-action Heal spell and inherited the properties from the 1-action and 2-action versions it would somehow simultaneously need to have a range of touch, 30 feet, and a 30 foot emanation.
I read it that it does not add the +8 to the 3-Action version. Look at the last line:
Heightened (+1) The amount of healing or damage increases by 1d8, and the extra healing for the 2-action version increases by 8.
It specifically only mentions the 2-Action version, not 2 or higher.