Good evening. Just had a question in regards to Cleric domain spells. Say I have a domain spell that isn't on the cleric list at level 2 (ie invisibility). I'm level 9, can I replace my level 3, 4, and 5 domain spells with my level 2 domain spell?
Lastly, if I had a lesser rod of extend would it work for the level 4 and 5 invisibility slots?
"Each day, a cleric can prepare one of the spells from her two domains in that slot"
Technically, "one of the spells" implies any, "from her two domains", implies that you would be able to prepare a 2nd level spell in the 5th level slot for domain spells (just like you can prepare a hold person on a 5th level slot, wasteful but you can). But it is up for debate.
As for the lesser rod of extend, since invisibility is a level 2 spell, it would work. You are expending a higher level slot for a lower level spell, it doesn't change the spell in any way shape of form. The rod doesn't care about the used spell level, only the original spell level.