ESP Direct commands

https://arduino-esp8266.readthedocs.io/en/latest/esp8266wifi/readme.html

using include ESP8266WiFi.h the following core cmds work for me

Serial.print("ESP.getBootMode(); ");
Serial.println(ESP.getBootMode());
Serial.print("ESP.getSdkVersion(); ");
Serial.println(ESP.getSdkVersion());
Serial.print("ESP.getBootVersion(); ");
Serial.println(ESP.getBootVersion());
Serial.print("ESP.getChipId(); ");
Serial.println(ESP.getChipId());
Serial.print("ESP.getFlashChipSize(); ");
Serial.println(ESP.getFlashChipSize());
Serial.print("ESP.getFlashChipRealSize(); ");
Serial.println(ESP.getFlashChipRealSize());
Serial.print("ESP.getFlashChipSizeByChipId(); ");
Serial.println(ESP.getFlashChipSizeByChipId());
Serial.print("ESP.getFlashChipId(); ");
Serial.println(ESP.getFlashChipId());
heap = ESP.getFreeHeap();