I have changed my email address and password for Icloud account, but it keeps on asking me to log in with my old obsolete email address .i do not know my old password

your original email address is your iCloud acct email, unless you changed the acct info. if you just mistyped, then retype because you could not get into a mistyped email address and get in. or is it a locked acct your are trying to break into?

Recover or Reset Forgotten Apple ID or Password on iPhone & iPad

This is all done on an iOS device and is often the simplest way to log back into an Apple account:

1. Open the Settings app and scroll down and tap on "iCloud"
2. Tap on the email address at the very top of the iCloud settings screen
3. Tap on the blue text underneath the password entry that says "Forgot Apple ID or Password?" where you'll have two choices:
   • If you know your Apple ID and don't remember the password, type in your email address and click "Next" to start the reset process
   • If you don't know your Apple ID, tap on "Forgot your Apple ID?" and fill out your full name and email address to recover the Apple ID login (yes, you can then do the password reset after you have the Apple ID)
4. Answer the security questions pertaining to that Apple ID, and follow the onscreen directions to complete the process

At this point you should be good to go, you can reset the password for the account and then login as usual.

From Apple:

If you forgot your Apple ID password If you're having issues signing in with your Apple ID password, use these steps to reset it and regain access to your account.
Your Apple ID is the account you use for everything you do with Apple, like shopping the iTunes Store, signing in to iCloud, buying an app, and more. To reset your password, you'll need to know the email address for your Apple ID. If you're not sure which email address it is, there are a few ways you can find your Apple ID.
Reset your password
After you reset your password
Get more help Reset your password You can reset your password when you go to your Apple ID account page and click Forgot Apple ID or password. Enter your Apple ID, then click Next.
After you enter your Apple ID, there are a few ways you can change your password:

Answer your security questions

If you know the answers to your security questions, select "Answer security questions" and follow the steps to reset your password.

Use email authentication

If you select "Get an email," we'll send an email to your primary or rescue email address that you can use to reset your password. Didn't get the email?

If you use two-step verification

If you set up two-step verification, you can use it to change your password. You just need a recovery key and a trusted device. Follow these steps:

1. Enter your Recovery Key.

1. Choose a trusted device. We'll send your device a verification code.
2. Enter the verification code.
3. Set a new password and select Reset Password.

If you permanently lost your recovery key or access to your trusted device, you can't change your password.

If you use two-factor authentication

If you have two-factor authentication, you can reset or change your password from your trusted iPhone, iPad, or iPod touch when you follow these steps:

1. Go to Settings > iCloud.
2. Tap your name.
3. Tap Password & Security.
4. Tap Change Password.
5. Enter a new password.

These steps will work only from a trusted device with a device passcode enabled. If you don't have access to a trusted device, you can reset your password when you follow these steps:

1. Go to iforgot.apple.com and enter your Apple ID.
2. Enter your trusted phone number and click Continue.
3. Enter the verification code that we send to your trusted phone number.
4. Provide any additional account information requested.
5. Choose your new password.

If you can't sign in, reset your password, or receive verification codes, you can request account recovery to regain access to your account. Account recovery will take a few days, depending on what account information you can give. After you reset your password After you reset your password, you'll be prompted to sign in again with your new password. You also might need to update your password in Apple services and on your devices. Get more help If you're still having issues signing in with your Apple ID and password, make sure that you're entering the correct Apple ID. In most cases, your Apple ID is also the primary email address of your Apple ID account. If these steps didn't help you change your password, contact Apple Support.Last Modified: Feb 19, 2016

If you need to change the iCloud account or Apple ID account on your iPhone, you must delete the existing iCloud account on the device. How to Change iCloud Email on an iPhone

You can go to iCloud.com and ask to have your password reset. You however must know what email account you used when you registered. iCloud will send you a link to your registered email account, follow the link and reset your password. Write it down somewhere.

Use a computer to log in to iCloud.com with your registered email and password to reset your account. Then log out of iCloud on the iPad and log back in with the new password.

Can you log in from another PC and change profile settings?

I can't help 'ya.
But I know who can!
Try this: Google ; Icloud - Account - Apple Support.
OR: Icloud: Apple - id - Apple Support.
If you can't find your answer yourself on one of those pages.
Then - You can call 'em or email 'em about your problem.
All info as how to do this is on both of those pages.
Your 'problem' is easily fixed - Don't worry:) !
C. (DK).

If it is an apple tablet that has Icloud and find my ipad on you can log in to his icloud account and change the password at Icloud.com