Should missed Sunnah prayer be made up?
Making up missed voluntary acts of worship is from Sunnah.
What is the ruling on a person who isn`t able to fast due to old age, or an incurable disease?
Paying the ransom is due on such a person, and that is giving a Mud (600 grams) of wheat, or rice, or the price of that amount to a needy Muslim for each missed fasting day. And Allah Knows Best.
Is it permissible to perform Tayammum for a month due to a medical condition that requires avoiding water?
Tayammum is permissible so long as the above excuse lasts. And Allah Knows Best.
Is love allowed or forbidden in Islam?
All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
If love refers to the involuntary inclination of the heart, a person isn`t held accountable for it; however, whatever follows this in terms of gazing, meeting, and the like is forbidden. And Allah The Almighty Knows Best.