i2C question on Wire.onRequest()

hello. knowledge wire.onrequest() allows send send data master on request. if want request 2 different types of data?
for example,

master request slave 'ok' on start up. after that
master request again slave input data.

code: [select]

void startuptest()
{
  wire.requestfrom(8, 4);
  while (wire.available())
  {
    char starta = wire.read(); // receive byte character
    serial.print(starta);         // print character   
  }
}

void requesta()
{
  wire.requestfrom(8, 6);

  while(wire.available())
  {
    float = wire.read();
    float displaya = / 255;
    serial.print(displaya);
  }
}

void loop() {

  startuptest();
 
  while(1){
    requesta();
 }
}

was wondering if above code work?
therefore question is, how let slave know difference between first request , other request?

no, because not compile without code. please post whole code only! http://snippets-r-us.com

but assuming setup serial.begin() , wire.begin() (and place startuptest() instead of ugly while(1)), kind of. how slave know difference between first request , other request?

and float single byte not going work float 4 bytes

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