You are doing a good job.
Wanted to ask one question.
I have used 6.7.6 LTS(most stable[written on SonarQube site]) version, it gave me some no of bugs and code smells. I fixed it.
Later on i just upload same code on SonarQube 7.4 version and this is giving different report.
So please suggest/recommend which version should I use.
Why you are saying LTS version is most stable?
LTS version is more stable because major bugs and vulnerabilities are back ported, which is not the case for intermediate versions. We also spend a few weeks working only on bug fixing prior to the LTS release.
That said, you should definitely have a look at the following topic if you want more details about differences between LTS and intermediate versions.