Little help here, as I am unsure. I own both Hitman 1 & 2, and have pre-ordered 3. What I want to know is, do I need to have 1 & 2 installed on my PS5 to play their missions through Hitman 3?
never really looked into this, and before anyone asks…yes I have both 1 & 2 installed on my PS5 as I was just as in the dark about how they work together as I am about this 
All you need to know is here:
Except, that does not answer the question of:
Do I need to have it installed:
HITMAN 3 will take up approximately 60-70 GB of storage space on all platforms, with the obvious exceptions of Stadia and Switch. The data that you download will also include all the content required to access HITMAN 1 and HITMAN 2 – but you are still required to own/purchase access to those games. To underline that; purchasing HITMAN 3 does not grant access to the previous two games by default.