Cracked or broken screen

Yes, it's recommended. Cracked glass keeps weakening every time you handle it, shards can cut, and moisture getting in through the crack can damage the panel underneath - a much more expensive repair than a simple glass replacement.

Yes. Face ID relies on the TrueDepth camera module in the notch, not on the screen itself. As long as that module isn't damaged separately (a drop on the top edge, for example), it keeps working normally after a screen change.

On some models, the brightness/True Tone sensor is paired in software with the original screen. A quality part that is properly recalibrated fixes this - which is why the choice of part and technician makes the difference.

It's a sign that the panel itself is damaged, not just the glass - common after a knock even with no visible crack. On most Galaxy phones the glass and panel form one block, so the whole module has to be replaced.

A knock can damage the digitizer (the touch layer) without breaking the glass on the surface. It's a common fault that is easy to identify during the diagnosis before repair.

Yes - Samsung's hidden diagnostic menu (dial *#0*# in the phone app) lets you test multitouch, dead pixels and vibration, useful to confirm how far the problem goes before a repair.

That usually points to a badly reconnected touch ribbon or poor-quality adhesive during a previous replacement - an installation problem, not a problem with the part itself.

No, it's an informational software notice on some Xiaomi models when the screen isn't the exact factory part - it doesn't stop normal use with an equivalent quality part.

It's often the screen connector (a ribbon knocked loose) or the backlight, not the motherboard - a fairly reassuring sign that points to a simple repair.

No - LCD, AMOLED and their variants have different costs and sensitivities. The diagnosis tells whether only the outer glass or the whole module needs replacing, which has a big effect on the price.