First of all, there is no scheme, such as JKPMSSS. The scheme which is provided to students of J&K and Ladakh (earlier J&K) is PMSSS (Prime minister special scholarship scheme). Now coming to your question, If you haven't taken admission to the allotted college and wanted to change the college, you need to fill the float option before the next round of counseling and If you haven't filled, I think then you cannot further participate in counselling and you need to take admission otherwise your seat may be get cancelled.
You can check: https://www.aicte-india.org/sites/default/files/FAQ_PMSSS1920.pdf -- Question No. 2 is similar to your question.
Although, I have participated in PMSSS counseling in 2017 that time we have offline counseling. So I have tried to answer up to my knowledge someone who has participated later in online counseling can let you know more on this.