how to undo changes made in run configuration

how to undo changes made in run configuration

actually i created a new run configuration (for eg) config_1 and that was
working fine till yesterday. Today when i changed the name of the project
to project_2 the old project name in the run config->classpath->user
entries (i.e) project_1 seems to be like in closed state and by mistake i
deleted it. now i cant run the program due to the class not found
exception. If i even add the project by clicking advanced->add projects
the program is not running correctly. How can i run the program or how can
i add the project??? Or if i even undo the changes made through local
history will that actually undo changes made in run config???