How to make an iPhone 4 have problems?

I need it to have problems, don't ask why

Dip it in the water n take it out really fast that way it will still work but have problems

You can to to brick it if you do it won't turn on until you unbrick it

Do a full restore and unplug it in the middle of it.

Pop in in the microwave for couple minutes on full power? That should sort it out.