folder espbasic 3.0 is ultimate basic and find what modify and how install
Inspired from esp8266 webupdater arduino examples (to add web update)
You can compile webupdate mini and flash to esp8266 ... after connect with esp8266 over wifi ...
and open http://192.168.4.1/update and upload ESP8266Basic.ino.generic.bin over the air
You can upload over the air again WebUpdater.ino.generic.bin
You can modify code and with Arduino menu sketch >> export compiled binary and load with http://192.168.4.1/update
https://docs.google.com/document/d/1NMZvnnjZ5XNzkykINgYS_Ql6mQ3nJEAzYudbmScdiIg/pub is ESP8266 Basic Language Reference
For ESP Basic 2.0 aXX
You can upload espbasic in classic mode same as https://github.com/costycnc/costycnc-espbasic-adjust-errors
Also you can upload espbasic original from https://github.com/esp8266/basic
some examples wifi mode https://github.com/costycnc/costycnc-WIFI_AP-WIFI_STA-WIFI_AP_STA-esp8266