Short runtime, "Service Recommended", or a swollen battery lifting the trackpad.
Charge cycles. A swollen battery is a hazard — don’t charge it.
A new battery and a charge-cycle test.
It depends on the model and on what we find inside, so we quote each repair individually. The diagnosis fee depends on the device, and you approve the exact repair price before any repair starts. If it can't be fixed, you only pay the diagnosis.