Who is responsible for shipment or courier when ordering an item?

Q: I ordered an item from overseas. When ordering, they offer you various shipment options, such as couriers, post office, etc., with various pricings.

1. Does this make me responsible if the post office loses the item, because I chose who I want to deliver the item to me, making them like my wakeel to accept the item and transport it to me. However, on the other hand, the seller still remains in control of the shipment since they sent it. For a lost parcel the seller will have to contact the post office and submit the claim, etc. not me.

2. The parcel disappeared, it seemed to be lost. The seller sent a new item by courier, which reached me within a week. The seller (non Muslim) will make a insurance claim for the 1st item from the post office. Can I use this 2nd item they sent me?

3. A few months later the first item arrived in the post. However customs want a payment of R1000 to release it. I need this shipment to be sent back to the seller because I have already received the 2nd parcel they sent, and this is extra. Who will have to pay for the return shipping and customs fees?

Fasting on only the 10th of Muharram due to some valid excuse

Q: I have read that it is makrooh tanzihi for one to fast on only the 10th of Muharram (without also fasting on the 9th or 11th). My questions are:

1. What is the ruling if one could only fast on the 10th due to some valid reason?

2. Should he rather not fast on the 10th?

3. What constitutes a valid reason?

4. What's the meaning and ruling of makrooh tanzihi?

Paying back a loan to the heirs of the deceased after the death of the creditor

Q: I borrowed 40000 US dollars from a friend of mine in America in 2008, which was equal to Rs 2500000 at that time. Our verbal agreement was to return the money in dollars. I could return $33000 through money changer, then there was a ban to transfer of dollars to another country. My friend passed away in America. I informed his family about the remaining amount and requested to collect that through someone travelling to Pakistan. After that there was no answer. I sent a registered letter on the given address but that letter returned to me as there was nobody to receive it. There had been correspondence on that address. I tried to trace them by other means but could not find them. Three years have passed. The Dollar rate has increased more than double. Please advise me in this regard.

Marrying a married women

Q: I married a girl and she was already married to a guy. For the last 4 years he was in a jail due to some reasons... The family members doesnt have any information about their son. And his wife also dont have any information about her husband whether he is coming out or not. There was no information at all regarding her husband so we had done nikaah. Is it right or wrong? Is she still married to her first husband? Her husband was calling from jail and he was not saying whether he was coming out or not. Now after 4 years he came back to India. What must do?