Questions about subscription to Creative Cloud

[#1]

I setup a brand new account and am about to decide on with applications to subscribe to.

Am I allowed to, for example, start with the Lightroom and Photoshop package and two weeks later, upgrade to the ALL APPs package? How will that affect billing?

Conversely, can I "downgrade" using the above example?

Or am I stuck with one package given that the plans are annual?

Will the subscriptions include the moble versions

[#2]

I have never tried to change a plan, so this is the only link I have

Upgrade single to all Cloud https://helpx.adobe.com/creative-cloud/help/upgrade-change-plan.html

[#3]

You can "downgrade", but that involves cancelling the subscription, so you might have to pay a cancellation fee.

If you're not sure, you're better off starting with a monthly subscription so you can cancel it anytime and choose a yearly subscription once you know what you need.