Is it true that whoever prays Fajr in congregation will be under the protection of Allah until the evening, and does forgetting the morning remembrances affect that?

Persevering in the congregational Dawn prayer at its appointed time is a sign of goodness. Forgetting the morning and evening remembrances (adhkar) carries no sin, as they are sunnah (recommended) and not obligatory. It is, however, desirable to make up for any missed ones, based on Al-Nawawi's statement: "Whoever has a prescribed remembrance and misses it, should make it up and perform it when able, and not neglect it."