LiquidCrystal_I2C.h library differences, same name, but not compatible?

Using Arduino Programming Questions
#1

Ive seen at least two methods of handling commands for LiquidCrystal_I2C.h.

Would this initialization be specific to ceratin libraries?

 //Using: https://github.com/fdebrabander/Arduino-LiquidCrystal-I2C-library
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);


void setup () {
    Serial.begin(57600);
    Wire.begin();
    RTC.begin();
   RTC_DS1307::get()

lcd.begin();  
 lcd.backlight();
 lcd.setCursor(0, 0);
#2

This is the one you get from the Arduino library manager:

#3