That will only work as long as the check clears. Anyone relying on those 'friends' better hope China never stops sending those checks. Ask the US or the USSR how that goes.
Well, sure, but like our ports and other infra that they bought up, that's what they are doing everywhere, so the checks can stop, and they retain ownership of all the economic bottlenecks
No, if things get bad enough, locals have a way of terrorizing any stable uses of those infrastructure. Again ask the US and USSR. What the hell are the Chinese going to do, perform a Gaza on the locals?
Not the poor countries that China supposedly "owns". Countries like Pakistan can't even keep the lights on. Why would they care about rare earth magnets? China provides gifts and in exchange Pakistan provides a pinky promise that will disappear as soon as the checks stop. They can't control their borders much less their crazies. And those crazies will terrorize any Chinese that try to start shit and will make it impossible to reliably take advantage of any infrastructure that China may want to use.