What needs to be done to achieve world peace and mutual cooperation for humankind and how long will it take?

If you already have a strong community which has brought about change, you do not need more. Merely continue to be a strong community and deal with problems which are bound to arise at a local level, and you will keep bringing about change. For example, even if the current generation is into good things, the next generation of your own always have the chance of calling you a bunch of fools for not exploiting the vulnerable; they will call themselves greater than you eho came before (a common trend; people like to fool themselves to seem less pathetic to themselves and, they hope, others). What you built is then destroyed from the inside.

When you force 'change for good', revolution or otherwise, you bring about the 'perception of change' rather than change itself. All the problems are actually swept under the carpet, out of sight. It just happens that is the very reason for a lot of the biggest problems in the world right now; even if all the visible people take on the banner of legitimacy and say there is no problem, there is no doubt among the people who have been pushed in the lower, oppressed corners of each region—out of sight—of the injustice and cruelty caused.

The end goal, if you want world peace, is the change in yourself, itself. You don't need to go outside and make your place a 'platform' for change, because the world is not generous. They will, instead, definitely focus on destroying your 'strong community' than being open to the idea of change. Rather, the existence of such a community is enough to incite hatred.

If you use the mentioned 'platform' for change through co-operation, the wicked of the world will only see you as fools. Their methods have worked for them; causing pain for others for their own gain has led them to lead better lives, in their opinion. Each and every one of my own family is like this; they instead take every opportunity to co-operate as an opportunity to harm. The 'neutrals' who go along with the flow, getting them to your side is not a victory either. It just takes evil to be dominant again (and evil likes to try to dominate) and they switch sides all over again. The change is superficial. On the other hand, go the violent route, and you will find it quite impossible to not succumb to the idea of the necessary evil, and the lesser evil, to prevail. But when you do this, all you do is 'sacrifice' those who are even less powerless. You are not so much removing evil as much as replacing evil with another evil. There is a real tendency in such cases to do the same as the evil predecessors have done; but from the other side. You may have destroyed those ones in the process, but in the end you essentially joined their hand. It is a real sore topic for most because trolls also like to maliciously bring up this point, but did the revolutions of the world really end all problems completely, or did they sweep many problems out of sight to claim victory for many of the previously oppressed, essentially befoming opponents to the rest? Of course, the method I mentioned also aims at non co-operation, but it aims at ending the idea of having gains at the cost of someone. It keeps making it harder to do that till it becomes impossible; to survive, such evildoers are forced to do better then. At the very least, I can say with confidence that if you have enough of such people who do not have power over anyone while not letting people have power over them, it becomes impossible for such a place to start an invading war. Rather, starting war is usually a means to distract one from a place's internal problems; instead they will be forced to deal with the same problems as they're thrown in the faces of the people who cause them rather than pushing those problems out of sight so they can say they live good lives—and invade so they can distract themselves, when they have nothing better to do. In the end, instead of people saying how problems are impossible to be fixed, you have people actually solving problems because they also have a stake in it; they're no longer able to push the problems they create on others and be done with it.

Instead of an 'external' problem, it is the 'internal' problem. Limiting yourself to making a strong community itself is the problem, whereas if you see yourselves as part of one world; after you bring about change in yourself, you continue living in a good way which forces other people to live in a good way if they want their problems to end. It literally speads like an infection till people cannot do evil anymore. The reason sustained world peace is impossible is because there will always be the next generations who will think themselves superior for exploiting the vulnerable, and there will always be places where people give up instead of following through with trying to be good; accepting the lesser evil at the cost of 'a few' instead. The grim reality that no one talks about is all the problems in the world, a very big portion, I'd even say most of it, is caused because we live in a world which has chosen a lesser evil over and over again. If people simply chose 'no evil' over 'lesser evils', the bigger evils would be stifled enough that they couldn't run around free doing, essentially, whatever they want. The current big evils are, almost always, born out of the lesser evils of the past, rather. And the current suppressed are from the powerless who were on the wrong side—the cost of past 'peace'—instead of the wealthy and the evildoers, like the ones choosing 'lesser evil' in the last claimed.