How many types or classes of stars have we discovered, and how many more classes of stars are there likely to be that we haven't yet uncovered?

Which classes of stars are most likely to promote the development of life? What are their current ages, and how long will they exist for? (Are we "early"?)

How much will JWST contribute to our understanding of star/exoplanet habitability? Will we get a better sense or even bounds on the possibility of life in our galaxy and beyond?

Have we found any exoplanet with similar properties to earth yet (temperature, mass, gas spectra, etc.)?