Intercourse during the day in Ramadan is haram for men and women while intercourse during the night in Ramadan is allowed. For more, please see the detailed answer.

If a Muslim misses fasting for many years, he/she has to ask Allah for forgiveness and repent to Him, and has to fast the days that he/she missed and feed one poor person for each day. If he/she is poor and cannot feed others, then fasting and repentance is sufficient and he/she does not have to feed others.

If a man shakes hands with a (non-mahram) woman during the day in Ramadan, and he ejaculates, his fast is invalidated. He has to repent to Allah from this sin, refrain from eating and drinking for the rest of the day, and make up for that day’s fast later on.