Can we cache the ad and display it when there is no internet connection?
I have read the sdk specs and it seems that it doesn't say anything regarding the offline mode...
These is what I've read : http://sdk.revmobmobileadnetwork.com/ios.html
Also if somehow caching is possible, will it generate income?
Yes you can cache the ad and display it whenever you want, but if there is no internet connection, RevMob's servers won't be notified and it will not generate income.