1.You can get this type of error if your class' .m file is not listed under the "Compile Sources" step of the "Build Phases" tab of your target. Normally Xcode does this for you, but sometimes it loses the plot and you need to add the .m file manually.
To do this:
TargetSettings -> Build Phases -> Compile Sources -> add your .m class ->Build and Run
2.Sometimes those errors appear because some framework is not linked properly. Just check all frameworks in "Link Binary With Libraries" in project's build-phase tab.
3.framework is same as project.release/debug