There aren't any specific way that you can tell if a project is scam or legit. But the points that you have discussed here would actually be a valid way to see if something is scam or not. Then again it does not give the full picture. Despite being a good project for years, it could eventually scam people in the end.
Everything we are talking about are centralized and everything could happen to them at any given moment. For this reason, it does not matter how much the research you do, is the people involved in that project our scheming a scam then you can literally do nothing.
It's good to be cautious about everything. But if you send a little bit of suspicious behavior happening in the project, you should exit. Giving a second thought in altcoin market is the stupid idea.