Memes

That's mostly for police. Once you're in court and ordered to testify, the person talking about germany is mostly correct. You can't be forced to self-incriminate nor testify against a spouse. Otherwise yes. Generally 99% of courts won't bother even asking the defendant to testify because self-incrimination is practically guaranteed. Usually only if the defense calls on them, which is often a bad idea.

Only if there’s a risk at incriminating yourself, and if it’s not immediately apparent how you’d run that risk (e.g. you’re a witness that doesn’t have a direct relation to the crime at hand) you’d have to motivate how it could be incriminating.

It's illegal to lie to the court. Even if all oaths weren't utterly worthless, one made under duress is inherently invalid. This one serves literally no purpose other than to psychologically dominate a person.

That doesn't give them the right to jail you indefinitely. This system lies and tells you we all have rights, but if they can just do that forever because you insulted or angered a judge, then you need to realize it is just a lie and we don't have rights. It's the same authoritarianism people fought and died to erase from the world. Judges can't be allowed to just do what they want.