During the pre-debut reality show KQ Fellaz American Training, the group released a song composed and produced by Hongjoong titled "From".

[7] From March 2020 to February 2025, Hongjoong released 8 songs by artists that he covered and interpreted in his own style (adding his own lyrics and arranging) under the project name "BY.

[8][9] The covered songs included "Space Oddity" by David Bowie,[10] "Purple Rain" by Prince,[11] "Black or White" by Michael Jackson,[12] "모처럼" by Yoon Jong-shin,[13] "Numb" by Linkin Park,[14] "Lemon Tree" by Fools Garden,[15], "Wonderwall" by Oasis, [16] "Beat it" by Michael Jackson.

[17][18] Hongjoong and fellow Ateez member Yunho were selected as the new DJs for MBC's Idol Radio Season 3, which aired from September 8, 2022, to December 27, 2023.

[20][21] On March 11, 2024, singer Chungha released her digital single "Eenie Meenie" featuring Hongjoong, who participated in writing and composing the song.

[24] Hongjoong and fellow Ateez member Jongho took part in busking variety show 나라는 가수 'Moving Voices' im Germany for KBS2's, which aired from November 2025 to January 2025.

[26] Hongjoong reformed clothes, experimented with various fashion styles throughout his career, often incorporating elements that challenge traditional gender norms.

This led to fans creating fundraising pages on the Polished Man's website, resulting in the collection of hundreds of dollars in 2019 and early 2020.

[39][40] In November 2022, Hongjoong donated ₩10 million (US$7,658.95) to World Vision Korea under the name "Atiny", the group's fan base.

On May 20, he was appointed to the 'Bob Pierce Honor Club', an accolade designated for major donors who have contributed over ₩100 million to the NGO and have displayed empathy towards various global issues.