One option is to contact Instagram support to see if there is a way to change the phone number on your account. However, it’s possible that this may not be possible given the confidential nature of Instagram user data. Another possibility is to visit the Settings page on Instagram and update the phone number information directly from there.
There is no definitive answer to this question, as it depends on the specific features and capabilities of the Instagram 2021 app. However, one possible scenario in which an individual could not change their highlight cover on Instagram 2021 would be if the feature was not available or options for customizeizing highlight covers were limited.