if a believer died by committing suicide, will he necessarily go to hell, shall he never be able to enter paradise one day? Can no one intercede for him? What if his parents or close ones built a masjid or Madrassa etc. In his name, or pass on rewords to him via zikr, recitation of Quran sahrif, duas or any other charity or good deeds? Would he not get any benefit from these many things? Would he face torture of the grave and never be relieved from it despite the above measures?
All praises are for Allah and peace and blessings be upon Allah’s final Prophet (SAS) with Allah’s help, the following is the answer to your question:-
One who has committed suicide and has died upon Imaan and Islam will be severely punished in the hereafter.
However, on account of Imaan, he will one day come out of hell. Only the unbelievers and polytheists who died in the state of kufr and shirk will remain in hell forever. (Fatawa Mahmoodiya vol. 1 pgs. 667,668)
A person can intercede for him and can also do acts of Sadaqaat for him. Hence, his parents or close ones can build a masjid or madrasa in his name. They can recite Quran and duas etc. and pass on the rewards to him (as in Isaale thawaab). Insha Allah, with Allah’s permission, he can benefit from these. Based on the sin he committed, punishment has been mentioned for him in the grave and in the hereafter. He will eventually be relieved and will not remain in the punishment forever. However, being forgiven and relieved of the punishment at any time on account of the measures taken, are all for Allah to decide. (Fatawa Mahmoodiya vol. 9 pg. 247).
And Allah knows best,
Mufti Waseem Khan