I didin't find a way how to use lock and unlock on the node, can you tell me?
someone's model have only one node, with it locked, and it is not a subnet, how did he approach this?

With the display flag on your sop, right-click on it in the viewer and choose “Delete History”. All that does is turn on the lock flag and then deletes all the sops which are input to it. This works because once you lock a sop, it never recooks again, thus allowing you to do anything you want including deleting its inputs. Note however though that if you now unlock the sop, everything will be lost.

thank you. so , if it just a model, is it equal to use file sop to import the file?

pretty much. but i prefer that method and keep my model progression in one hip and another with an imported bgeo of the final model.