Firstly, is the error occurred in transport block same all the time so that number of subframes is the major contribution to the curve of BLER ?
Of course, bit errors occur randomly in the simulation. However, you have to make sure that the number of simulated subframes is sufficiently high, such that the BLER results are meaningful. For example, when simulating only 100 subframes, the lowest BLER that can be obtained is 1/99, meaning only one out of 100 transmitted blocks was in error. This result is statistically not reliable at all.
Secondly, is that any code file that deals with CQI mapping with Modulation Order ? I would like to modify the Modulation Order that matches with certain CQI value so that fix Modulation order will be used in certain SNR, , is it possible ?
The Modulation and Coding Schemes (MCS) associated with a certain CQI value is standardized by 3GPP. It is possible to modify the MCS for each CQI, you can find the implementation of CQI values in LTE_UL_load_parameters_dependent. Please note that link adaptation is performed when LTE_params.UE_config.CQI_fb = true, when an effective CQI mapping is performed as described in http://publik.tuwien.ac.at/files/PubDat_175708.pdf and http://publik.tuwien.ac.at/files/PubDat_186497.pdf . This means that just changing the MCS of certain CQIs will probably not lead to expected results.
Thirdly, what is the main difference between coded and uncoded output results in Throughput and BER plot ? How do both coded and uncoded operate to generate the output ? How come BLER plot do not have uncoded curve ?
Uncoded bit errors are considered for the calculation of the uncoded Bit Error Ratio (BER), meaning without turbo coding, while bit errors of coded data bits are considered for the calculation of the coded BER, meaning with turbo coding applied. If a codeblock still has errors after the decoding, it is counted as block error (or frame error) and is considered for the calculation of the Block Error Ratio (BLER) (or Frame Error Ratio (FER)). As these blocks are code blocks, there is no uncoded BLER.
Last but not least, how can i verify whether my throughput, BLER and BER plot curve are correct ?
For a quick check you can use the example results provided in the documentation in order to check if the simulator is working as expected. Beyond that, verifying numerical simulation results is a non trivial task. Whether results you produce with you own simulation are meaningful or show the expected or intended behavior is not straight forward to evaluate.