multisensor inputs?

how many input devices (sensors) is possible to connect to Arduino?

The Arduino has 6 analog inputs. If you're willing to put up with the loss of precision, you can use analog multiplexer chips to fan those out to several dozen.

For temperature, you can use sensors like the DS1820 series, and get several inputs on a single digital pin.

So, at least in theory, the answer is "more sensors than you can afford to buy" ;D

Ran