I am planning to buy a large screen TV to watch World Cup with intention to return it. Since in the aggrement clearly states that we can return without presenting any reason, it is ok for islamic sharia to buy and return to the store?

From Islamic point of view it is now lawful, because according to Islamic principles, the buyer has three days to return the item if he detects some defect in it. However, if there is no defect in the merchandise item he cannot return it after separating from the transaction place.