1. How do you successfully build a community around a blockchain project without revealing too much prematurely before building a strong enough community?
You cannot build a strong community around your project when people do not know what the project is about, you have to first of all build the project for people to see if there is an actual utility in it, and if there is people would want to use it and you can grow the community you want.
4. How can I establish trust within the community while maintaining security?
Quite a lot of people invest in new projects basically out of the hype and because they want to make money quickly, it is somewhat like gambling, they don't trust the project or believe in anything about it, they just buy many new projects and see which one yields them profit. Having said that, if you offer something unique, people might buy your idea, but whatever you want to launch should be able to service certain needs and it should be a new idea, not what many developers have tried and failed in. Prolly you might get people who would be interested.