Hello Gaurav,
The TM4C129 memory is 8KB sector size but then it spans over 2 banks making it 16KB (0x4000). Since you tried to erase 0x2000 onwards the entire region from 0x0 to 0x3FFC is erased. Hence please move the code to 0x4000 onwards and then erase from 0x4000 onwards.
What you need to jump to the application code by loading SP with content of 0x4000 and PC with content of 0x4004. You can write a simple inline assembly code like
ldr sp, [0x4000]
ldr pc, [0x4004]
Regards
Amit
