> How Can I learn about assembly language for apple devices?
> Is it the same X86 Assemly as it was for intel processor in windows?
You must mean, "Apple Desktop computers" here. Look at your system configuration in "About this Mac"; mine says "Intel Core 2 Duo". That's a regular Intel (X86) chip.
>what assembler should I use?
Any Intel compatible one you like. The thing to watch for is what sort of executables it can produce, i.e., you can write a Windows program in assembly but it won't do any good on a Mac. The assembler (or, more likely, the linker) manual ought to tell you if it can write Mac OS compatible binaries.
> What about other devices like iPad or iPhone?
> Which assembly language should be used for them on A5 & A6 chip?
ARM RISC code, which is *awesome* by the way. However, I don't believe these devices are easily accessible to run your homemade software on. In addition, just about any of the interfaces -- wifi, screen i/o, touch opertaions -- need an interface library. I don't think there are any ones for the iPhone/iPad since Apple relies on developers to work through XCode using Obective C.