CCS/MSP-EXP430FR5994: Can CCS be coded in any C or Embedded C language

They are hard to understand if you don't understand the embedded processor. But it is all C. DriverLib and RTOS provide some abstraction. It sounds like you might want to look at Energia if it supports your processor. They do all the hard work and leave a very basic level that is easy to use.

But I think it best to start at the basics and work up. First get a blinky to work, that should be easy to understand - especially if you use DriverLib. Then build up the other pieces you need for your project, like the UART.

Finally, there is a lot of help available on the MSP430 forum where they can guide you through any specific questions about this processor.

so sir
what is driver lib and how can it be used
could i code in c in driverlib

without you explaining why / what is so hard for you to understand, it is difficult to point you in the right direction.

At the most basic level, embedded C is no different from your "regular" C. The only (minor) complication are those device-specific macros that simply point to certain memory addresses for you to write to or read from in order to operate the peripherals. Those macros are essentially pointers that have special names to help you read and understand them.

the single biggest challenge to any embedded C programmer is the willingness and ability to read and understand the datasheet. After that, everything is peachy.