Is the feeling of remorse and self-blame after the death of one's mother, due to the son's shouting at her and his actions, considered undutifulness (ʿuqūq), and is not kissing the parents' hands daily also considered undutifulness?

What is said or done by a child in moments of boredom or anger is not considered an act of disobedience (ʿuqūq), provided that their general disposition is one of dutifulness and kindness towards their parents. Allah overlooks such matters, in accordance with His statement: "Your Lord is most knowing of what is within yourselves. If you should be righteous, then indeed He is ever Forgiving to the often returning [to Him]" (Quran 17:25). What happened on your part is not considered an act of disobedience or the cause of your mother's death. You can atone for any shortcomings by supplicating for her, giving charity on her behalf, honoring her friends, and maintaining ties with her kin, as mentioned in the hadith (definition) narrated by Abu Usayd Malik ibn Rabi'ah Al-Sa'idi.