1. No*, DNA40 and DNA200 dont fluctuate when you hit the fire button, but YIHI and some other china temp control chips do as they display the Live ohms. The Evolv DNA chips always show the resting resistance.
2. No*.
3. The DNA40 will if the resistance has change too much, not sure how much exactly, sometimes i can take a tank off to fill it and it will ask, other times it wont, depends on how hot the tank is and how cold the room is to cool it while its off the mod.
The DNA200 is configurable, the default is 25% which ive left mine at and it works similar to the DNA40, maybe not as sensitive.
4. See 3.
5. On both the DNA40 and 200, the resistance can change up or down .01ohms depending on if the ambient temp has raised or lowered, not an issue.
Neither chips have every asked if my coil is new or old unless ive removed it from the mod, on a Very few occasions its done in if ive removed the batteries to put in a fresh pair.
IF your mod does this often, you may have a bad contact or connection, make sure your 510 and threading is clean on both the mod and the atty, also ensure your coil leads are securely trapped in the atty.
* As stated in #5, sometimes you can see the resting resistance has changed by 0.01ohm, this is down to a change in ambient temp and normal.