Can I change my iCloud email

The main address on your iCloud account - something@icloud.com - may have additional versions (i.e. with the same text before the '@') of @me.com and @mac.com, depending on how long you've had the account. Apple refers to these alternatives as 'aliases'; you cannot change them.

Once you have created an iCloud account and chosen an @icloud.com address to go with it you can't change the address (short of creating an entirely new account).

However, all is not lost. You can add up to three 'email aliases' - these are additional addresses (not accounts) which deliver into the same inbox as the main account. (In fact it's a good idea to give out alias addresses, rather than the main address, because if they attract spam you can easily change them.)

You should be aware before you start that once you've created an alias you cannot turn that address into a full iCloud account or move it to another account.

More information on aliases here: Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

As to the spam, set up a Rule in Mail to move all messages to your primary address to the trash, from which it will be automatically deleted after a week. Go to https://www.icloud.com and sign in. Select 'Mail'. Then click the small cogwheel icon at the top of the left panel and select 'Preferences'. then select 'Rules'.