It’s generally a bad idea to create and use a different AppleID. Notwithstanding the loss of access to paid Apps, Services and Subscriptions (these being forever linked to the AppleID from which they are purchased) doing so creates all manner of difficulties for your data and Apps. It is always preferable to update your AppleID account as your details change - keeping your primary/secondary email addresses, trusted phone numbers and security details current.
To recover access to (and use of) your older iPad, you must concentrate on recovering the AppleID and associated password used for last activation - as without this, the Activation Lock that inhibits use will not be resolved.
Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
Turn off Activation Lock – Apple Support
As you will discover, unless you are the owner of the AppleID that was last used to activate the device, or unless you can secure the cooperation of the previous owner, you’ll not be able to defeat or bypass the Activation Lock. Without documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple won’t assist - and nobody here will be able to help you.
If you are the owner of the AppleID that previously activated the device - and you have forgotten your AppleID or associated password, these can be recovered here:
https://iforgot.apple.com
To recover your credentials, you’ll need access to one of the following:
- Your primary email address mailbox that corresponds with your AppleID
- Any of the secondary/recovery email addresses that should be configured for your AppleID account
- Any of the trusted telephone numbers (fixed line or Cellular/Mobile) that are associated with your AppleID
Unless you AppleID account has not been fully/correctly configured, or has been seriously neglected, recovery of the AppleID and password should not be difficult.
More information about recovery of your AppleID:
If you forgot your Apple ID - Apple Support
More information about recovery of your AppleID password:
If you forgot your Apple ID password - Apple Support
When you recover access to your credentials, you would be well advised to log-in to your AppleID account from a web browser - and verify/update any email addresses and trusted telephone numbers:
https://appleid.apple.com
