User Activity

After purchase. Seller has sent me a ebay message with a web site to buy from him. By passing ebay in the future. Is he allowed to do this by ebay rules? Or is that frowned upon?
When a seller sells an item. Does he have to have it. Like can I sell on ebay, a bar of soap lets say.. Then if I get a buyer. Go to the shop buy the soap. Put in the a box and post it? Is that allowed?
Buying I am using Australia Post Parcel Collect Service.Where my address is the Post Office with a 10 digit ID number.When my parcel arrives they send me a txt to come and collect.Instead of the old method of leaving a card in the letterbox.And going...