Quote Originally Posted by Steve Jeff View Post
1. Let's say I took off, climbing at 65kts and there is a 15 kts headwind. If at 100ft, SUDDENLY the wind direction changes and becomes a 15 kts tailwind, my airspeed will suddenly drop to 65-30=35 kts, right? I guess it will end up in a spin and being too low to recover...
No because a light plane will react to the 15 kt change in airspeed almost immediately. It's unlikely you would notice. Your speed over the ground would change by 30 kts, however.

2. On final, I encounter an updraft, I noticed that updrafts are +Gs, so is this scenario at risk for an accelerated stall?
Yes, an updraft would + load the airplane, for a second. Then the plane would respond to the gust by ballooning above the desired glidepath, not much else.