Using the millis() function with button

Using Arduino Programming Questions
#1

Hi, I am currently doing a project using a button , an led . i am having some trouble coding . My objective is that if the button is press within 5 sec the led will blink for 1 sec 3 time . and if the button is not pressed (after 5 sec ) the led will blink for 500ms 3 times .
here is my code:

int led=4;
unsigned long previousMillis = 0;
const long interval = 5000;
int btn=5;
int btnstat;
int i=0;
int x=0;

void setup()
{
  pinMode(led, OUTPUT);
  pinMode(btn,INPUT_PULLUP);
}

void loop()
{
   digitalWrite(led,HIGH);
    delay(5000);
    digitalWrite(led,LOW);
 unsigned long currentMillis = millis();

if (currentMillis-previousMillis<interval)
{
    previousMillis=currentMillis;
  btnstat=digitalRead(btn);
  if (btnstat==LOW)
  {
 
    for(x=0;x<3;x=x+1)
    {
    digitalWrite(led,HIGH);
      delay(1000);
    digitalWrite(led,LOW);
    delay(1000);
     
    }

  }

}
  else 
  {
 
     
    for(i=0;i<3;i=i+1)
    {
    digitalWrite(led,HIGH);
    delay(500);
    digitalWrite(led,LOW);
      delay(500);
      
     
    }
  
  }
#2

wait, so what problem do you have?
error messages?

#3

I am using this millis function in another program so this is just a simulation( the led on for 5 sec at the start of the program simulates my other program ) . when i reach the if else function if just skip to the else function without having the option to press the button.

#4 
int led=4;

What does this mean? ledPin means something.

    delay(5000);
    digitalWrite(led,LOW);
 unsigned long currentMillis = millis();

delay() and millis() rarely belong in the same code. currentMillis is a stupid name. The variable holds the time that some event happened. The name of the variable should reflect that event. In this case, now is a MUCH more appropriate name.

You MUST determine when the switch BECOMES pressed, NOT when the switch IS pressed. THAT is the event that is important.

#5

you can adapt the code from this section:

 if (digitalRead(buttonPin) == LOW) 
      {
        pulseBegin = millis();
        while (digitalRead(buttonPin) == LOW){} //do nothing while push button is being pressed
        pulseWidth = millis()-pulseBegin; //record pulse width of button being pressed    
        if (pulseWidth <5000){} //turn off if the button is pressed less than a second
      }
#6