Is Error State (http://chdk.wikia.com/wiki/Canon_error_codes , http://chdk.wikia.com/wiki/FAQ) in vers.req screen last error occured,
Yes.
If my camera have E18 error, is it possible that the camera is ok, just lens has been blocked one time?
Exactly.
Is it possible for camera to display more than one error in vers.req screen?
As far as I know, the camera only displays the latest error. Previous entries may be preserved in the camera's ROM, but those are not displayed.