purchase

Q: Is it permissible for one to purchase a grave for oneself before one's death?

Q: What is the ruling regarding the following situation:

At the time of Qurbaani, certain stock farmers sell sheep and goats to the public. They charge a stipulated fee for providing the services of skinning the animal, slicing and parceling the meat for all those people who wish to do Qurbaani at their farm. Before the days of Qurbaani, people go to the farms, and after selecting the animals, purchase them from the farmers. After purchasing the animals they leave the animals on the farms to be slaughtered during the days of Qurbaani.

Other people merely phone the farmer and purchase their animals over the phone without going to the farm and selecting the animals. At times, the farmer selects and marks an animal for the client (e.g. sheep, goat, etc.) and concludes the transaction over the phone on the specific marked animal. At times, the sale is concluded over the phone, however the farmer does not select and mark any animal at the time of concluding the sale. Since the farmer knows that he has extra animals in the pen, he concludes the transaction on an unspecified animal with this in mind that on the day of Qurbaani, he will select an animal for the client and carry out his Qurbaani.

Is this method of purchasing the animal and carrying out the Qurbaani correct where the animal is not selected by the purchaser but by the farmer himself according to both situations explained (i.e. where the farmer concludes the sale on a specific marked animal or on an unspecified animal and only specifies it at the time of slaughter)? If this is not the correct method of purchasing, then what is the correct Shar’ee method of purchasing the Qurbaani animal and asking the farmer to slaughter it on one’s behalf?