Does the prayer become invalid by not listening to the Imam's recitation in audible prayers, and is it sufficient to listen to only part of it?

The prayer is valid whether the congregant listens to the Imam's recitation or not, because not listening does not invalidate the prayer according to most scholars. The preponderant opinion is that reciting Al-Fatihah is obligatory for the congregant in both audible and silent prayers, and consequently, the prayer is not valid without reciting Al-Fatihah.