iPhone 5 iCloud Activation Lock (Apple ID Locked)

You have several, compounding issues. To remove the lock you need the information used to sign into the phone. However, you also have a disabled account because of trying to guess the password. Then you also have forgotten security questions and also can't really utilize some of the other things needed to prove to Apple that you are the account owner (which in all honesty you are not)

The easiest route is if you forget about the account and can prove ownership of the phone. Apple provides a website link for doing this (this was already provided to you but for some reason you rejected it). I have never seen anybody say they can do this on the phone.

- https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof. Prior to this new online service Apple typically required the original receipt issued by Apple or an Apple Authorized Reseller and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership). 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.

Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support

I'll just add that in my opinion if you can't get this done, an iPhone 5 isn't worth it. I use old Apple equipment myself but even I have realized that anything of that age is almost useless unless all you need is a mp3 player. Even then, the battery is likely not going to last long between charges. I have an old iPhone 5S but on my next trip to an Apple Store it is going with me for recycling.

You probably do not have enough information about the account to be able to recover the account itself. This is deliberate because of all the people out there trying to hack accounts.

Your only likely solution now is to ask Apple to reset the device using the service mentioned earlier. The only other thing I can think of is if your grandfather is deceased. For information about how to request access to a deceased family member's Apple account data, and possibly their equipment, read this support article --> How to request access to a deceased family member's Apple account - Apple Support

Unless you have the account information that set the lock, the original receipt from Apple, or can demonstrate legal inheritance from a deceased owner, you cannot remove the lock; recycle the device. Frankly, with an iPhone 5 it would not be a great loss.

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. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."

Is your grandpa the original owner of the iPhone and can he provide valid proof of purchase information? If so, , he can start an Activation Lock support request at Apple