DATA BACKUP from SQL Server Express to SQL Server 2012
Yes. The database format is identical across all editions. An Express Edition database for sure can be restored on a non-Express Edition (you fail to mention whether is a Standard or an Enterprise Edition). The other way around it may be subject to restrictions, Express Edition will refuse to attach or restore a database that:


exceeds the size limitation of Express Edition
contains Enterprise Edition only features, like partitioned tables. On SQL Server 2012 anything from sys.dm_db_persisted_sku_features  will block an Express Edition. This restriction was lifted on SQL Server 2016 SP1.


It is important that both servers (the Express Edition and the non-Express one) be at the same version.