Code emulation and copyright infringement?

You have raised several complicated issues with respect to copyright/software law and I advise you to seek IP counsel with respect to these matters...

How can an inventor give up his rights? Or transfer them to someone else? Writing a statement is enough?

I strongly suggest you contact and seek the advice of a patent attorney regarding issues concerning inventorship versus patent ownership.

Are there specific lawyers for creative intellectual property?

An intellectual property attorney will be able to advise you in ascertaining your rights in any and all types of intellectual property.

Do I own my code?

Not sure if your asking about ownership of the original or customized code, please clarify.

Probably not as the building is a rendering of the copyrighted element in the Cinderella movie, seek copyright counsel for advice on this matter.

Can two trademarks with identical names and international classes exist, if they specify different products under the class?

Since the mark "up" is being used in the apparel class 25, the goods are too closely related so no another company cannot trademark it for similar...

Can I market and sell a T-shirt that has a photoshopped image of my company's CEO printed on the front?

The CEO has a right of privacy and you may need to get permission. However, contact a copyright attorney to review your shirt as the final shirt...

I have an intelectual property question.

Character names are trademarked not copyrighted but you should seek counsel of an intellectual property attorney to examine your work and the work...

Someone is threatening to use my work as their own, without permission. I have recorded all communications concerning this.

Yes you own a copyright in your sketches regardless of formal training and if you want to enforce this right seek the counsel of a copyright attorney

Is it illegal to promote restaurant specials on your own website without the restaurant's consent?

As long as there is no false advertising and the special did occur there isn't a problem