If I buy a physical copy of FH2(second hand), am I still able to play the game? Does that mean I can’t access to any DLC?
You can play the game normally with the disc, yes.
To access DLC you need to find a code online in store’s old stock.
Search for Forza Horizon 2 Car Pass or Storm Island.
In the gamestop website you can get the ultimate edition digital that comes with VIP and Car Pass. You will be missing Porsche and Storm Island.
Wait - a code for the DLC? But they’ve retired the DLC. You can’t buy it through any way, period.