Slight grooving can be normal, but deep grooving is not. The depth of acceptable grooving is specified by the manufacturer.
The squealing is usually due to lack of hi-temp brake grease on the back of the pads to absorb the high frequency vibration that we hear as squeal. Sometime high humidity conditions can cause this too, but only temporarily.
The use of anti-rattle clips and a small amount of hi-temp brake grease on all contact points of the pads with the caliper stops any additional noises.
At every service, the caliper slider pins must also be lubricated and checked for smooth operation, something that is quite often overlooked.
For example: Permatex 24125 Ceramic Extreme Brake Parts Lubricant (others are available too)