Here’s your chance to start DoOverLingo!
Yeah, no.
The current Duolingo French course does eventually get to the real future tense, but not until Unit 64. Unfortunately, there is no very convenient way to jump ahead, so you have to slog through 63 other units before you get there, and that might easily take you months.
As for grammar lesson, Duolingo has what they call “guidebooks” that provide some very basic grammar information. They’re easy to overlook but they’re there. For example, see the guidebook for Unit 64. Not all grammar topics I might wish for are covered by guidebooks. I found I learned more grammar from clicking the “discuss” button on questions I got wrong. Unfortunately, the powers that be in their infinite wisdom disabled new comments and questions there, so it’s not as helpful as it used to be. The old questions and answer are still there and are still helpful.