Does the policeman has the right to put handcuffs without a permission?

They have the right to handcuff you for safety reasons.

Yes, if they feel that you are dangerous.

Yes, they have that right.

Basically, yes, the police officer can put handcuffs on someone who is under investigation if the officer feels that the person should be detained until the police have investigated further. Police do not have to get 'permission' to enter an apartment under several circumstances, but in this case it appears that the police were called about a domestic disturbance and they had reasonable suspicion to enter to investigate and /or prevent escalation of an alleged incident.

The police can enter the apartment without your permission if they believe that somebody's safety is in jeopardy. If they heard arguing or if there were reports made of serious arguing then that may be enough. He would need an experienced criminal defense attorney to review the reports to make sure, however. The police can always put handcuffs on you anytime you are placed under arrest. They do not need your permission to place handcuffs on someone they are arresting. Otherwise, no one would ever give them permission and the police officer's safety would be placed at risk.

No, the police don't have to ask your permission to handcuff you. If a neighbor calls the police because they hear fighting or shouting coming from your apartment, the police can enter your apartment if they believe a crime is being committed and they must enter in order to save someone from being harmed.