How likely is it for other planets to develop reptilian/insect/mollusc/mammal life?

Not likely at all. Bacteria sort, or maybe Tardigrades, something impervious to temperature, pressures, radiation, that sort,,maybe.

Odd creature the water bears, surviving 10 days outside the ISS, vacuum of space, radiation, and 200 degree minus. Anything else and PFFFT.

Impossible.

"Animal" is a form of terrestrial life. You're not going to find that independently developing anywhere else.

1 out of 400,000,000 planets will develop some type of life.

Other planets in our solar system? VERY unlikely. On certain exoplanets, pretty likely, though with a different chemical composition. For instance, they could not get our diseases and vice-versa.