Insert a SIM card eject tool or a paperclip into the small hole besides the SIM card tray, located on the upper section of the left edge of the phone.
Press to eject the tray.
This may require a significant amount of force.
When reinserting the SIM card, ensure that its contacts are facing to the rear side. The tapered corner of the SIM card has to point to the outer bottom corner of the tray.
Peel back the Kapton tape from the remaining three ZIF connectors, then use a spudger or your fingernail to lift the hinged retainer clips on the ZIF connectors, and slide the cables out from each.
The third ZIF connector is mostly underneath the motherboard. When reassembling your device, make sure it is placed back underneath.
I replaced the battery now but encountered a problem, as my phone wasn't working properly afterwards. When I switched on, it kind of reset to default and the play store app kept crashing, so I had to do a factory reset