1) No, you can (at least with fw 1.00.0900).1. You can't power on while charger plugged in
2. Try remove your battery and then press power button twice with the second press you need to hold until it powered up (battery only)
To power off press twice, with second press also hold until it off
Dji use first press just check battery power level, while the long second press is for power on/off
3. What do you charge the spark with ? I mean what is the charger ? You need at least QC 2.0 charger that can charge @12V, check your power adapter, look at output voltage, if it is original and not faulty, it can charge properly, don't use any iPhone charger since it only 5V for all iPhone that available right now.
If all ok
2) Seems to me OP do it correctly in its video.
3) No, 5V charger are also ok, no "must have" for 12V, it just take more time. I tried basic wall charger 1A and 2A, power pack 2A and all worked. For sure the one at 1A was delivering only 0.9A (4.5W), with 2A was 1.9A (10W). With the DJI charger that come to the Spark, I got 12V and 1.5A (18W).
So with the DJI one as reference, using a standard 5V/2A adapter will charge the battery in 2 x DJI tiime, 5V/1A with 4 x DJI time.
In all cases, I was able to power up the Spark but of coarse I cannot turn on the motors or take off.
