The first question is discussed in this topic:
To the second question, I think it's technically required to do as you suggest to be perfectly legal if you are concealed legally in State 1 which prohibits OC and then enter State 2 where you can OC but do not have a license to CC.
Can you name the two states you're talking about? If it's Utah, Nevada, Idaho, Arizona, just OC the whole time. If you prefer to CC, just unconceal before entering a state where you may not conceal.