Violin and Wedding Ring

[JASTŻOMB]

Is violin (after i give it to musican u know) or wedding ring usefull somehow?

[MazyRun]

They are just story items. Story items feature in various different ways (and some don't always have a particular mechanic or usage related to them)..

The violin is an example of a significant story item (with a usage), its possession dictates which way the story branches (i.e, there are alternatives to giving it away and alternative outcomes).. However, not all 'story items' play a significant part in the game..

When the game was still in development there were several quest related or story related ideas that didn't quite come to fruition and/or were not fully implemented..

There are several examples of this throughout the game, you will find various objects that represent something that was intended to play a bigger part of the games story or something that used to be part of the game but no longer features in a significant way (but it can still be found within the parts of the game where it originally featured or was intended to feature)..

These 'lost' items just kind of exist as lore items now I guess. If you read up on the wiki about these kinds of items (wedding rings, odd stones, etc.) it all makes sense how they would have tied in to the game and existed as a quest item/story progression mechanic (or a general game mechanic relating to character progression).

First playhtroughs always leave a lot of intriguing lingering questions similar to the one you posed. It took me countless playthroughs (and studying the wiki) to figure out stuff like why some crates are un-openable and why some items seemingly have no use.