Does anyone know what the use of the Kin 1Y03 access card is? Would it be all right to buy a textbook without the access card?

Yeah you'll be fine if you don't have the access card.
I think the site had practice questions and some other resources, but you'll be fine without it. I don't remember using it a lot.
Just the lecture notes and textbook will be enough.

Alright, thank you!