Five precepts and lower realms My understanding is that, although we are practicing five precepts in this life, there is no guarantee we will not be reborn in lower realm, it is possible to take rebirth in lower realm in the next life or many lives after. But according some sources, when one practices five precepts that person will not be reborn in one of the lower realms (in the next life). Which one is the correct one?
Reaching at least the Sotapanna state is the only 100% guarantee of not being born in lower realms ever again.

But if you reach at least the second insight knowledge -Paccaya Pariggaha Nana of the 16 stages of insight towards becoming a Sotappanna, it is said that you will not be born in a lower realm in the immediate next life.

If you are a devout Buddhist who keeps to the five precepts, it is highly unlikely to be born in a lower realm in the next life. But there's no guarantee. It mostly depends on the quality of your precepts. As in how well you keep to them.