How to combine common articles and nouns in a phrase

Hello, I have seen different constructions to combine common words to avoid repetition, but I do not know which one(s) are grammatically correct. For example:

Original: We explain the differences between the conception phase and the production phase.
1. We explain the differences between the conception and the production phases. (omission of the first common noun + pluralization of the second common noun)
2. We explain the differences between the conception and production phases. (omission of the first common noun + omission of the second article + pluralization of the second common noun)
3. We explain the differences between the conception and the production phase. (omission of the first common noun).