The OTC market for foreign exchange is indeed much larger than the exchange traded futures market for FX. Therefore statement I is correct.

Delivery-versus-payment (DVP) arrangements make sure that title to a security passes only when payment has been made, and these arrangements, usually implemented through national clearing agencies such as the DTC in the US, help avoid the risk of counterparty defaults.

Electronic Clearing Networks (ECNs) offer cheaper trading costs than exchanges, in fact that is their primary attraction. Exchanges offer other advantages, but lower trading costs is not one of them.

ISDA master agreements provide templates that a large number of OTC market participants use to standardize their OTC trading activities. Therefore statement IV is correct.