The second option is more correct: Merry everything & happy always. however, we do not usually say happy always. i would say merry everything and i wish you happiness always. What is the difference between happy born day and happy birthday ?feel free to just provide example sentences.

Happy about (something). Yes, in portuguese (brazil), you can say feliz dia de ação de graças to wish someone a happy thanksgiving. Dia de ação de graças is the direct translation of thanksgiving, and adding feliz.