When I lock my 2011 Tuscon from the inside and then use my Key to unlock it it sometimes sets the horn off and takes for ever to get it to stop beeping. Any suggestions on what could be wrong?

Every car brand and model has its procedure to stop the flashing light and alarm sounding.
But still the common procedure is Make sure boot and bonnet are closed properly.

It can also be a switch, but check your alarm by locking yourself inside the car, and then press the close button on the key 2 times repeatedly until the lock control on the door doesn't make anything. Then open the door by pushing the lever or open the hood . If the horn sounds and the lights blink your alarm is ok , if only the lights blink you should take it to dealer. You can stop the hazard lights and horn sound by pressing the unlock button on the key.

There is an issue with the battery connector coming un-soldered at the circuit board inside of the remote.

Sounds like the body control module is going bad. Need to be sure, not cheap.

if your key is not working to unlock door==try turning key over and then try to unlock door. I have had keys made for replacements and they sometimes don't work quite right one way but work just fine the other way.

to unlock hood with out being able to get inside; you need to reach up from under car and pull/yank on cable to unlock hood.

it will be in the horn contact /ring/pin under the steering wheel. probably no contact to complete the circuit .

I would start by replacing the FOB. Sounds to like the electronics inside it are bad. The only reason the horns would go off is if you hit the panic button. There is a slight chance the receiver is bad. But Fobs are cheaper to replace than the receivers. If you have two FOBs and they both react the same, then replace the receiver. Or just ditch the system. The keys (in the door locks) should still activate the alarm system.

Unlock all doors, foot on brake, all doors closed. Cycle key quickly but carefully on-off appr 10 times until the car honks one time.

Do not turn the key far enough to start the car, just to the 'on' position so the dashboard lights up.

When the horn honks, open and close the driver's door, press any remote button and that's it.

Program another remote? Quickly open and close the driver's door again and push a button on the 2nd remote. That's it.

When you're done, remove the key and the horn should honk 3 times. You're all set.
Sometime it takes more than 10 on-offs to set program mode. Open/close the door, lock/unlock etc, wait 10 minutes, then try again

Security engaged, Lock and unlock doors with key until horn stops.

immobliser problem ,,,,, or a crash switch has tripped ,,,,try turning on ign and disconnect and reconnect the battery,,, be careful to do it without making slow connections for fear of sparks and leave door open for fear it could lock up ,,,, u may have to lock and unlock using remote after,,, hope this helps

Setting can be accesed through the radio to change options. Follor the owners manual.