I've setup 2 node cluster vsan and with a witnees host.
I usually run only one node and keep synchronized every night by open another node, after that i let one node in maintance mode and shut it down.
I thought one node can be another's backup. Now one vmdk object on running node have an unrecoverable mistake, can I get this object from another node? and how to do it?
Auto synchroning should be disabled though, and how to do it?
This is not the intended use of VMware vSAN. VMware vSAN is designed to provide you with HA storage for VMware cluster and in case of two nodes, that's active-active mirror. You should not turn one of the nodes on and off and turn it to active-passive synchronization.
VMware vSAN does distributed object storage so your VM's vmdk is comprised of two components and a witness distributed between disk groups and hosts.
In other words, you're picking a wrong tool to do the job. If you want backups, use proper backup software like Veeam, Veritas, or any other or if you need DR, there is vSphere Replication.
