The remedies for such patent infringement are civil and not criminal, so you will not be arrested. You may run into other laws, but more information of the subject matter is needed before advising. Each of these ideas had only one of the components that my idea needs to make it work. Consider an eraser which could morph from the lead or lead sheath of a pencil like device, you might indeed have patentable subject matter as a process, for a utility device, and for designs. Whether it can be made, produced economically, is merchantable in various markets, are other questions.
Most patents being granted now a day are for some combination of prior art elements.
The more the merrier. Whether or not you can get a patent for combining only two prior art elements depends upon the following factors. How long the need has been recognized but remained unsolved. Market success can also be used to overcome obviousness rejection as well as affidavits from experts, etc. When there is a connected effort of many, we are able to make ourselves heard and have a positive outcome on the issue at hand.