Inability to update or install apps because of disabled apple account

So this question apparently doesn't really have anything to do with an Apple Account but is really about whether or not to upgrade your iPhone? You can decide whether or not to upgrade your iPhone. That will depend upon various factors including desire for security and desire to be able to run the most recent versions of apps. If you do decide to upgrade then your device will automatically and irreversibly upgrade to the newest iOS version it will support which will be iOS27.

This support article has instructions about updating an iPhone or iPad wirelessly --> Update your iPhone or iPad - Apple Support Read the article for recommended criteria for being able to use wireless updating.

You can also use Mac and PC computers to update system software --> Update iOS on iPhone - Apple Support

If your old Apple Account was permanently locked by Apple then you may discover the Find My/Activation Lock will block you from using a different account on your iPhone. Refer to How to remove Activation Lock - Apple Support There are only two ways to remove a lock:

#1 If you have the necessary information, you or the signed in owner can do this yourself by simply signing in with the owner account and password information and doing as instructed in the above article. Clearly this method will not be available to you since the old account is not working.

#2 Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they “may” require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community and chat with Apple indicate that typically Apple will absolutely require, and ONLY accept, an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support

You do NOT have to be the “original” owner. In the case of removing the lock with the correct information, it can be anybody who knows the currently signed in account information. In the case of asking Apple to unlock it, as long as you have the original Apple receipt (which may well not have any personally identifying information on it) you are okay. Apple confirmed this in a conversation.

If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.

If you cannot get the device unlocked then read this section from the very bottom of Apple Trade In - Apple :

"Does Apple offer recycling?

Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free."