Is there any emulator for linux which fully supports apple iphone/iphone/ipad apps? Any other way to run such apps on linux?
Currently the only emulator for testing iOS applications is build for MacOS.
There is a work in process to bring an emulation software to linux which you might want to take a look at...but judging by the development status it'll be a while till it's usable.
EDIT: This is outdated information. The project was discontinued some time in 2013.
For real productive development work I'm afraid you won't get around buying Apple hardware.