Is receiving money in a PayPal account, with a 30-day hold period imposed on it, considered a legitimate form of possession (qabḍ) when exchanging currencies, and is it permissible for the transferor to receive the agreed-upon amount immediately or after the hold period expires?

For currency exchange, possession in the same session is required, based on the Prophet's (peace be upon him) saying: "Gold for gold... hand to hand." Paper currencies have the same rulings as gold and silver. Possession can be actual (hand to hand) or constructive, such as depositing into an account. If the money enters your account, the other currency must be entered into your account within the same session. However, if the money remains with a broker, he must pay you the money immediately upon its entry into his account.