[Rehan]

I completely understood the post.Maybe nobody will explain like you did.I am very thankful to you.When i failed in Option 1 i decided to use option two.I successfully upgraded to Debian 9 Stretch.After installation before doing anything i thought i should reboot the vps first.I used the command "reboot" and it cause the shutdown of VPS.I waited for 30 minutes but server did not logged on back.So i request a OS reinstall.Now i have Ubuntu 16 and server is running properly.
Thanks for your great effort.Atleast i understood what is the problem and why is it.
I don't think the topic needs more reply.I have requested a thread close.If you ( @Hidden Refuge ) have any further words to say about you can simply PM me if you don't mind.

@arsalahmed786 you can lock the topic.

[arsalahmed786]

Thread closed as requested, Thanks "Tech Consultant" (@"@Hidden Refuge") for supporting our users. As OP said you can PM him. If anyone of you think it should've be reopened please ping me once.