Or if a person commit suicide in Kasi, will such person get Moksha?
In Chapter 26, Description of Manikarnika, Kasi Khanda Purvardha of Skanda Purana, Sri Vishnu says Self-killing is not allowed at Manikarnika Ghat and it cannot bestow Moksha.
74-76. Let those other rites (Sandhya Prayers, holy ablutions,Tarpana, excellent study of Vedas,etc) too, performed excellently and with faith, be the bestower of salvation. Barring Prayopaveśa (fasting unto death), no one shall indulge in self-killing. O Išana, let those rites be the cause of ultimate salvation. After performing a noble rite even on some other occasions, the devotee should neither boast about nor regret it. O İśa, with your blessings let all those holy rites bear everlasting fruits here. O iša, with your grace let everything concerning him be of never-ending benefit.
So, at Manikarnika of Kashi above rites bestow Moksha but not suicide. One must live with Dharma as mentioned in many chapters of Kasi Khanda of Skanda Purana to get Moksha in Kashi. Also, one can clean off sins only if they take dip in Ganga with faith and devotion. Hindu scriptures never recommend Suicide. This answer explains punishments for Suicide.