(Mythic domain: When determining the effects of your domain's granted powers, you're considered 4 levels higher. This increases the effects of powers you have access to, but doesn't grant you powers at a lower level than normal.)
A) Is there a level cap on this (usefull for multi-class characters but nothing else) or does this extend the effective level beyond the characters max?
B) When a character has both Mythic Domain AND Magical Knack (Oracle), do they stack provided the character has at least 2 other levels in another class?
(Mythic domain: When determining the effects of your domain's granted powers, you're considered 4 levels higher. This increases the effects of powers you have access to, but doesn't grant you powers at a lower level than normal.)
A) Is there a level cap on this (usefull for multi-class characters but nothing else) or does this extend the effective level beyond the characters max?
B) When a character has both Mythic Domain AND Magical Knack (Oracle), do they stack provided the character has at least 2 other levels in another class?
A. There is no level "cap" beyond what you can naturally attain. That is, your base can't be any higher than 20. Any other modifiers, such as from the Mythic Domain ability, would stack past 20, so you would count as Level 24 for the purposes of determining the effects of your Granted Domain Powers.
B. Magical Knack only applies to Caster Levels. In other words, it really only applies to your Domain spells. Mythic Domain specifically mentions Granted Powers, which are things like your Fire Bolts, Bit of Luck, etc. These things are mutually exclusive of each other. An increase in Caster Level does not affect your Domain Powers, and an increase in effective level for Granted Domain Powers does not affect your Caster Level for Domain Spells. So in a way, they stack, but not on the same subject.
It's also important to note that Magical Knack does not increase your Caster Level beyond your total Hit Dice. It's a great trait if you were going to dip into a class for a couple levels.
Perfect, thank you very much! That is exactly what I needed to know.:)