> Force charging-Charging even after reaching 100% in battery backup.

I guess you mean tickle-charging: Keeping the the charger attached, so the battery keeps being held at 100%. This is indeed not the best you can do 

> Charging only after the battery empty.

It's common that people believe that full-cycling (charging only when empty and then completely) batteries extends their lifetime. While this is is true for Nickel-based batteries, all modern laptop batteries as Li-Ion. Full-cycling is the worst you can do to such a battery, because they hate both being empty, and being full. They last longest when kept half-charged.

> Charging parallel while working.

Charging while working is no different to the battery from just being charged electrically. But the heat caused by the Laptop adds to the heat from charging. Heat is what Li-Ion batteries hate most. It will reduce their lifetime. However, if the Battery is thermally well seperated, this should not be a problem.