Hello Dhanalakshmi Sreerama,
Thank you for your question and for your interest.
Actually the newest KSDK version is 1.3, you have older one.
Supported devices you can find at Release Note, which is at <ksdk_path>\doc folder
Unfortunately, at the moment there is no KSDK support for MK20D in 50MHz (MK20DX128VLH5).
Best Regards,
Iva