Attach 110(2012) from SQL Server 2014 Instance to a (110) SQL Server 2012 INSTANCE
You can't do this. Compatibility mode makes no difference here. You simply can't go back to 2012 from 2014 via backup/restore or detach/attach. 

Your options are limited to either generating scripts to recreate the schema and objects or using a third party tool. Red gate have one but I've never used it.