What is the ruling on delivering remittances at the exchange rate prevailing at the time of agreement versus the time of delivery, in order to avoid Riba (usury/interest)? And what is the ruling on lending an amount in one currency and repaying it in another currency, given changes in the exchange rate? Is that considered Riba?

It is impermissible to exchange currencies except by mutual possession (qabdh) at the contract session. The possession by an agent is considered possession by his principal. It is not permissible to lend one currency with the condition of recuperating it in another currency, because that is a deferred exchange (sarf mu'ajjal). However, if the creditor and debtor agree on the day of repayment to settle the debt in a different currency at its exchange rate on the day of repayment, there is no harm in that. It is not permissible to lend a person on the condition that he exchange his Riyals or transfer them through the lender, because that is a loan that draws benefit.