One of the major changes that you will face when you move from on-premises cloud to the public cloud is the switch from capital expenditure (buying hardware) to operating expenditure (paying for service as you use it).

Box 1: No

With the pay-as-go model, you pay for services as you use them. This is Opex (Operational Expenditure), not CapEx (Captial Expenditure). CapEx is where you pay for something upfront. For example, buying a new physical server.

Box 2: No

Paying for electricity for your own datacenter will be classed as CapEx, not OpEx.

Box 3: Yes

Deploying your own datacenter is an example of CapEx. This is because you need to purchase all the infrastructure upfront before you can use it.