1;WHY Do we have projects that places restriction for investors from certain regions.
It's because they have certain rules and regulations that they have to obey base on their geographical location. Not just because crypto is meant for everyone, they are also good in breaking the rules of law of their country.
2;Why do some project owners ban some regions from participating in the Marketing campaigns of their project but Rather allows such people to invest in their project.
I'm not aware of this, if for the marketing maybe they already have someone or a certain agency dedicated for the marketing on that specific region. Since they are allowing investors from that region to invest that's the closest possibility that I can think of.