The nine types of devotional service are mentioned in Śrīmad-Bhāgavatam (7.5.23):

śravaṇaṁ kīrtanaṁ viṣṇoḥ smaraṇaṁ pāda-sevanam
arcanaṁ vandanaṁ dāsyaṁ sakhyam ātma-nivedanam

iti puṁsārpitā viṣṇau bhaktiś cen nava-lakṣaṇā
kriyeta bhagavaty addhā tan manye ’dhītam uttamam

“The process of devotional service entails hearing, chanting and remembering the holy name, form, pastimes, qualities and entourage of the Lord, offering service according to the time, place and performer, worshiping the Deity, offering prayers, always considering oneself the eternal servant of Kṛṣṇa, making friends with Him and dedicating everything unto Him. These nine items of devotional service, when directly offered to Kṛṣṇa, constitute the highest attainment of life. This is the verdict of the revealed scriptures.”

As for being freed from all sinful reactions by chanting the holy name of Kṛṣṇa only once, one must chant the holy name without committing any offenses. Then chanting one name is sufficient to rescue a living being from all sinful reactions. Such a person who chants the holy name of the Lord offenselessly is very important and woshipable. Indeed, the nine devotional processes, beginning with śravaṇa and kīrtana, can all be attained at once if one simply chants the holy name of the Lord offenselessly.

In this regard, Śrīla Jīva Gosvāmī states in his book Bhakti-sandarbha (173): yadyapi anyā bhaktiḥ kalau kartavyā, tadā; kīrtanākhya-bhakti-saṁyogenaiva. Out of the nine processes of devotional service, kīrtana is very important. Śrīla Jīva Gosvāmī therefore instructs that the other processes, such as arcana, vandana, dāsya and sakhya, should be executed, but they must be preceded and followed by kīrtana, the chanting of the holy name. We have therefore introduced this system in all of our centers. Arcana, ārati, bhoga offering, Deity dressing and decoration are all preceded and followed by the chanting of the holy name of the Lord — Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare.