I am using visual studio 2017 and sql server 2016 for development of SSIS. I am in situation where I want to deploy my SSIS package to client side where old visual studio 2015 is used. So because of this I am not able to deploy it. So my question is how do I deploy my SSIS package to client side? Does downgrading visual studio from 2017 to 2015 affect my code?
SSIS projects are the same, as long as you install the latest version of SSDT.
Deployment has nothing to do with Visual Studio though. You need to develop your SSIS project targeting the same version as the production server. Many features depend on the target server's version. For example, SSIS Package Parts can only be used for projects that target SQL Server 2016 and above.
I've been using both Visual Studio versions on the same project for almost a year because SSIS support in VS 2017 was only a preview until recently. I had to wait until October 2017 for SSIS in VS 2017 to became stable enough to ditch VS 2015. Up until August 2017 there was a nasty bug that didn't allow me to open C# transformation tasks in 2017, so I had to switch to 2015 each time I wanted to edit them.
As I remember, diffing the project files showed that the only change from one VS version to another was a different version number in the file.
There was no one-way project upgrade between 2015 and 2017.