Q: AppleID

Hi. Take a look: Sign in with a different Apple ID on your iPhone, iPad, or iPod touch - Apple Support

All Apps are FOREVER tied to the Apple ID used to purchase them, & must be updated or re-downloaded using that ID. They cannot be transferred, by you, to a new ID.

You can call iTunes support, explain the situation, & see if they will transfer these purchases to your new ID...only they can do so.

Good luck.

If you forgot the password of the old Apple ID and are unable to reset it at iforgot then contact Account Security and have them reset it for you:

Contact Apple for help with Apple ID account security - Apple Support

As wjosten has posted, apps and digital content are forever tied to the Apple ID and in order to update them you will need the password associated with the Apple ID that was used to purchase said content.

Did you remember to sign out of iTunes on your PC & on the App Store?

I Have successfully changed the email used for my Apple ID & can update old apps easily & if you've done it that way there should be no problem, however if you've created a new Apple ID then yes previously downloaded Apps will be tied to that old ID.

and what if we don't have that access anymore.

should we delete all apps and redownload them?