We are at the end of our tether.
Our 1.5 year old male cat cries non-stop to be let out. This isn't easy as we live on the 4th floor and can only take him for walks 1-2 a day. As soon as he comes in he starts to cry to be let out again and this can go on for hours. We can't leave him out all day, as something could happen to him and spending 5 hours a night walking him is not possible either.
On top of that, he relieves himself on our carpets, floors etc whenever we do something to displease him. It's like he is punishing us.
Recently he even bit my sister for no reason. he sees her often and she takes care of him when we are away - so he is used to having her around.

He has been neutered and this has not helped in any way. We took him to the vet to check if it's a health issue and he is 100% ok. The vet only said that he is a naughty cat and we should get him more toys. He has tons of things to play with, a 3 room flat to run around in and gets taken for a walk every day... what more can we do?

This can't go on, my husband wants to give him away:(

Could it be that some cats are simply not made for life in a flat and must have access to the outside world to be happy?