Help how to remove fixed state

[josemendez]

 Can I do that at runtime not using any buttons?

Yes. Simply set the desired inverse mass values in case of fixed particles (0 for a fixed particle, any positive value for a non-fixed particle):
http://obi.virtualmethodstudio.com/tutor...icles.html

In case of pin constraints, just use the API to remove them:
http://obi.virtualmethodstudio.com/tutor...aints.html