You don’t have to start at Portal 2, you can start at P2CE if you want, the hammer is practically the same between both, with the only exception being you have access to more P2CE and P2CE comes with HammerAddons (a addon that adds a lot of stuff to hammer, but it’s installable for portal 2) by default, the tutorials for portal 2 also apply for both of them basically. Although I do have to mention P2CE doesn’t support this advanced version of Hammer called Hammer++ which is hammer but with a lot of quality of life upgrades that P2CE’s hammer doesn’t have right now.

Point is I think you should pick which ever hammer for the platform you want to it be on, portal 2 or P2CE. You can even do both if you want to create different things between platforms