YOU SAID:

an old dog cant learn new tricks unless it is wearing a disguise and is actually a young dog

INTO JAPANESE

老犬は変装して、実際には若い犬でない限り、新しいトリックを学ぶことができない

BACK INTO ENGLISH

An old dog can't disguise and learn new tricks unless it's actually a young dog

INTO JAPANESE

老犬は、それが実際に若い犬でない限り、偽装して新しいトリックを学ぶことができません

BACK INTO ENGLISH

An old dog can't disguise and learn new tricks unless it's actually a young dog