Correct spelling, explanation: shiny is the correct spelling because it is made from the word shine. Shine ends with e so when we add y to it, e is omitted. This is an orthography rule, so shiny is correct and shiney is wrong.

Definition of shiny:
adjective, bright, sparkling
I really like the shiny silver metal accents on the furniture.
This dress is too shiny, it’s more suitable for New Year’s Eve party.

Incorrect spelling, explanation: this spelling is incorrect because when y is added to a word ending with e, the vowel e is skipped. For example grease → greasy. And in the same way: shine → shiny. Not shiney, but shiny is the correct form.

Incorrect spelling

Incorrect spelling

Incorrect spelling