How to make Database to support Multiple Languages
What do you mean by "data is showing correct in the application (front end) but incorrect in database"? The database doesn't show anything, it stores the data and hands it back to you (your app) when commanded. If you used the right types, you're good to go as far as the data's integrity is concerned. The database's language doesn't affect storage but it will affect display and some tasks (e.g. sort).

Applications need to be able to handle the types, languages and fonts. For instance, if you use a version of TOAD that does that not support Cyrillic characters, it won't render the data correctly even though it is stored correctly in your database. That's why you see the ???????? when you retrieve non-ANSI character data.

Older version of TOAD did not support all Unicode characters and fonts by default (they did EASCII/ANSI); you needed a Unicode version of TOAD that had the right font support and/or the right NLS_LANG setting. Check your version of TOAD against their specs to see if you have both the language support and font support. 

It used to be a really weird dance getting the settings right between the OS, Oracle, TOAD, SQL*PLUS and whatever else you have running. That's largely gone with recent versions of the product stack. I think TOAD's been Unicode enabled since Toad 10 but please verify. If you are not or cannot get on the latest version, check out TOAD's documentation or the Oracle community in Toadworld for workarounds.