Beginner: How many inputs?

Thanks for all your advice!

Ouch. Seems quite advanced to get all those inputs?

But I am able to get 6 analog from one UNO?

What does "so there is only one ADC that is used by all analog pins" mean?

I've read about Mega now... "54 I/O (incl 4 HW UARTs, 14 PWMs, I2C bus), 16 Analog inputs"

Shouldn't the Mega do the job?