May I know if this version on GOG includes "Festive Seasoning" DLC?

Yes it's included :) (should've answered here, it'll be easier for people who may have the same question :P)

Yeah. Sorry I was rushed.

Is Festive Seasoning the same as Chinese New year DLC ? :O
If it is not, does overcooked 2 has this update in GOG ? Thanks in advance, kind regards!

I'm... not totally sure :P
So, I made some quick researches and found that it seems to be a specific DLC for Overcooked 2, and I think they're different.
What's inside each of them can be read here for :
"Festive Seasoning" : https://www.team17.com/overcooked-festive-seasoning/news/
"Chinese New year" : https://www.team17.com/overcooked-2-chinese-new-year-free-update-available-now/overcooked-2/

And for the question if it's included in GOG's version... I can't check because I don't own Overcooked 2 ^^" But there are very high chances since it's a free DLC, like the "Festive Seasoning" DLC for Overcooked 1. If you want a confirmation, I would suggest you to either create a specific thread to ask (people will see this question more easily), or simply ask to GOG's support.
Sorry for not being able to help you more, but still I hope I helped a bit :)
Cheers ! No problem ;)

A old question, but I asked myself and started the game to give a clear answer:

The Chinese New year is included in the Festive Seasoning which is free in Overcooked2.

Yes, it is included in Overcooked2.