That would completely depend on the specific year, make and model of vehicle. What are you driving? In general, if the automaker recommends a 225/45-19 sized tire for your vehicle any tire with a taller sidewall aspect ratio would cause a decrease in turning and cornering responsiveness. Your handling could get quite sloppy.

you can in most cases but you are already running a 19" rim. By going to the 45 series you gain about 1/2". going to the 55 series you gain about 1 1/4". This may seem minimal but that is all it takes to have rubbing issues..

You can, however you need to make sure the wheel wells can accomodate the tires, the front tires don't rub on anything when turning, calibrate your speedometer so it reads correct speed, and make sure the taller tires won't have any adverse effects on the ABS system.

What's the vehicle?

No one can give you a useful answer without knowing this.

yes

anyone?