IOS – Forgotten iCloud email ID and password

The easiest manner to check is from this web site:

• https://www.icloud.com/activationlock/

If that fails, the older method still works in all cases and Apple describes the steps here:

• http://support.apple.com/kb/HT5818

Expand the portion that says (in the english version) How do I check for Activation Lock before purchasing a used device?

It states:

Follow each of these steps to make sure that you can use the device you purchase:

Turn the device on and slide to unlock. If the passcode lock screen or the home screen appears, the device has not been erased. Ask the seller to completely erase the device by going to Settings > General > Reset > Erase All Content and Settings. Do not take ownership of any used iPhone, iPad, or iPod touch until it has been erased.

Begin the device setup process. After choosing a language, choosing a country, and connecting to a network, the device will begin activation. If you are asked for the previous owner’s Apple ID and password, the device is still linked to their account. Hand the device back to the seller and ask them to enter their password.

On iOS 7, the part where you are asked if you want to enter your Apple ID is the step that means it's not locked to another iCloud account. If you cannot enter your new Apple ID from the setup you will see a prompt to enter an existing password and can conclude that it's not released from the previous owner.

Since you're not getting to that step, either get a SIM card that satisfied the carrier lock on that device or perhaps connect it to iTunes and see if you can restore the device. In my experience, iTunes also checks if the device is locked and will tell you to remove the iCloud lock before it lets you restore the device when it's at the point where you can start the setup assistant.

Yes, you will be required to verify your account when you first log in.

I would suggest trying to get to the bottom of it BEFORE you upgrade, it will be harder after (since you should still have some access to email accounts etc).

Also, I would research the effects of running iOS8 on an iPhone 4S. Although it may be supported, I would think it would be incredibly slow.

I know you didn't ask for the second part of this answer, but I would strongly recommend you do some more research on this before blindly doing it.