Hi :) soo i found few melody items any suggestions what they do or maybe they do nothing at all?

It just depends on which items you're talking about. Some are books, minions, wearables, foods and some are just random items that do nothing but maybe sell decently in user shops.

for example tree luminar rock and strawberry melody

Strawberry Melody is a food and Tree Luminaire Rock is a toy. Generally, just clicking on an item in your inventory will show you all the options for it.

ok thank you :) have a nice day everyone

The Melody Item tag just means that they were given out by the daily Melody's Cottage during December. They're not necessarily more special than other items, and they'll do the same as any other book or food or something else on the site.