الجواب وبالله التوفيق

• Regarding the following ayat, Hazrat Mufti Shafi Sahib Rahmatullah Aleh has mentioned:

(نساء،۳۱) اِنۡ تَجۡتَنِبُوۡا كَبٰٓٮِٕرَ مَا تُنۡهَوۡنَ عَنۡهُ نُكَفِّرۡ عَنۡكُمۡ سَيِّاٰتِكُمۡ

“From this ayat it can be understood that the mention in ahadith regarding wudhu, salah and other aamal-e-saleh being the kaffarah(expiation/reparation), is pertaining to the gunah-e-sageerah(relatively smaller sin) only and that the gunah-e-kabeerah do not get forgiven without performing tawba(true repentance). That too is coupled with the condition that the person engaging in gunah-e-sageerah made every possible effort to refrain from (and leave) gunah-e-kabeerah. It can further be understood that if a person who is indulged in gunah-e-kabeerah keeps on just performing wudhu,salah and other aamal-e-saleh, such actions will not become a kaffarah for his gunah-e-sageerah let alone the gunah-e-kabeerah.”

• The method to perform tawbais includes:
  1. Immediately stopping the sin in which one is indulged
  2. Truly repenting from Allah Subhanahu Wa Ta‘ala on the previous sins
  3. Making firm intention to not indulge in such actions ever again
  4. If there was a fardh which was not performed due to such indulgence then perform it (if it can still be performed) or perform qadha. If the sin led to ignorance of huqooq-ul-ibad such as owing money to someone etc., such a right should be paid back or request should be made for forgiveness from the concerned person. If the ignorance is non-monetary such as irritating or mentally torturing someone or doing gheebat then forgiveness should be requested from the concerned person.
• The third section of your question has been answered as part of #1, all the rest is up to the absolute discretion of Allah Subhanahu Wa Ta‘ala.

واللہ اعلم بالصواب