Can you use a 4G SIM in a 5G iPhone

The 5G phones currently on the market are “backward compatible,” meaning that they are capable of functioning on earlier-generation networks outside of 5G coverage areas . Will a 3G or 4G phone continue to work? 4G devices will continue to work.4 May 2021

5G isn’t replacing 4G any time soon. In fact, they will coexist and work together. 5G capable phones can actually use both 4G and 5G technology .

After 5G network is commercialized, the 4G phones will still function normally. The 5G phones allows for interoperability with 4G/3G/2G network. Therefore, 5G phones work with 4G network, as same as 4G phones work with 3G network .