Spells have no effect on spells of higher level.
For example, you have an illusion spell of 4th level. It won't be revealed as illusion by a divination spell of lower level (even if normally, by RAW, it says it reveals any illusion).
An equal level divination spell can reveal it if the caster is of a higher CL.
Using a higher level spell slot to cast a lower level divination spell doesn't count. Applying metamagic to the divination spell to make it use a higher level slot also doesn't count. Heightening the divination spell's level by using Heighten Spell, does.
What's your opinion?
