1. What are the different between PIC18 and PIC32
PIC18 is one "stem" of MicroChips 8 bit controller family (there are more).
PIC32 is their 32 bit family (which you should stay away from for a long time).
2. I want to buy a KIT that have micro controller like PIC18 or PIC32 and also this KIT need have some sensors, activators, LCD screen, keyboard and / or other features
Also I want that this KIT will have some explanations about how to build and program him
Are you have any recommendations ?
Where I can buy these KITs ?
Did you try Google?
From the sound of your question, I'd advice you to get something allready built.
You'll probably have to mount sensors to any board you get, as no kit designer can know what exactly you need, so will at most make something generic or perhaps add an area of board for prototyping your own sensors.
I think you should start by reading a lot (say for a couple of months) on the subject, before you decide on any board - then you'll be able to make a better decision on what you need.