Encountered a new problem.

Loose connections is one of the reasons for very frequently varying battery percentages and "recharge battery" notifications.

The other problem with the connected middle pins is : Charging.
I do not understand why, but it gets charged at 3.8V to 3.9V. And discharged at 3.5V. + sudden "voltage percent" drop to 2% at 3.6-3.7V itself. (Good part about drop, it charges at 2A)

As asked, I logged the battery level, when not connected. Under heavy load, it has dropeed till 3.0V and recovered back to 3.3-3.5V, (sometimes consistently on 3.3V). Plus, though it says "not charging", I have been able to charge it 4.1V (I had to keep track of it manually).

Is consistent battery usage at 3.3V bad for battery ?
Do all batteries drop to very low voltages under load ?
Is it bad to charge it to 4.2V? ( it takes about 1.5-2 hours extra after 4.0V)

PS: Could not log it, but I think phone shut off after touching 2.8-9V under heavy load.