Plague Inc questions from a beginner

[Bronxsta]

Only four questions:

1) I've played quite a few times with bacteria and I usually end up with the issue of the whole world infected, a cure being worked on, but not enough DNA points to do much about it. I get a few lethal symptoms, then not enough points to get anything else and few if any points coming in, and can only watch as the cure is conpleted. Advice? (Not disease strategies, but how to get DNA late game) Do traits play a factor in getting DNA?

2) Is it wasting points to get cure-slowing abilities before the world starts working on a cure? Do the effects kick in when the cure research begins or it doesn't work like that? Haven't actually tried it, just curious

3) About transmission: for example, the rodent-bird vector eventually links up and allow for cross species/water-air for cross-substance travel. If I devolve prerequiste vectors like Bird 1 or Air 1, do you still maintain the effect of the more advanced traits? (Also applies to lethal symptoms, etc.)

4) I read in another forum about some traits "increasing the research goal." What does that mean exactly? And some traits say they slow the cure research but the progress only goes back like 1% then continues as normal. Do those trait have other effects? (Basically what effects do traits have cure development?)

Thanks