Hi Paul,
I2cdetect is only a tool to discover the presence of I2C devices, but it doesn’t do any thing else.
If you wish to do transaction at command line, the i2cset and i2cget is what you need, try “i2cget -y 0 0x4d” and see what it is returning.
python smbus is only a suggestion if you want to use python to control the bus.
One of the implementation can be found here : pysmbus/smbus.py at master · bjornt/pysmbus · GitHub
If you wish to write in C, you can open the I2C bus device as a file localed in /dev/i2c-0 for example, and doing some read/write operation on the device.
According, to the specs, ADC conversion seems to be started when executing a single write to the device and then reading it returned value.
For the LCD, you should look at its specs, there is similar transactions to achieve, there is probably severals registers to initialize.