//I'm afraid limiting everyone in the world to 2 children would not make the world population fall as its grown so fast already//
No it wouldn't. But it would stop the population growing any further. And if they took my advice to preferably have fewer than two, the population would decline. If those in the 3rd world cannot subscribe to the idea (and I'm quite sure they won't) they will have to get on with it. Meanwhile those of us in the 1st world will have to take more stringent measures to ensure those in the 3rd world remain there to suffer the consequences of their idiocy.
As far as I can see, Mr Rajapaksa's ridiculous idea was not done with climate change in mind. In was done mainly to prevent chemical fertilisers causing kidney disease (a theory that has never been proved). As a consequence of that I didn't mention climate change or net zero at all. But since you've raised it, net zero is a fanciful idea which a few well meaning - but perhaps misguided - academics have managed to persuade a few gullible politicians is a practical proposition. It isn't and never will be until all the substances that human beings can burn have either run out or have become too impractical to extract. Whether I think climate change is real or whether I care about it will have no influence on that.