Restoring accidentally deleted emails from iCloud backup on iPhone

I accidentally deleted all emails on iPhone and some are showing in trash bin but not all (older ones) and because I have iPad and Mac air they have been deleted on these.

all devices are backed up to iCloud , can I restore from yesterdays backup and will all the emails be there ?

If so how do I restore as the instructions say to reset back to factory settings - will this not delete the latest back up?

[Re-Titled by Moderator]

Original Title: Restoring emails accidentally deleted