i would say life on other planets (as inteligent as human or not... or more) is VERY possible and VERY likely imo. idk if there are any, but i do believe it is VERY possible
lol, you just repeated yourself 3 times.
on topic:
first off, are we talking advanced life forms? or simply life forms?
well, advanced life forms would certainly need some for of intelligence to be able to survive, however Intelligence as we know is mostly applied to the resources we have had as humans, such as opposable thumbs, so logically we could use these opposable thumbs and our fingers to have a firm grip on things, that is logic on our own type of resources.
Other life forms may not necesarily have those resources but different ones and according to their intelligence
in the form of logic + physical ability, use those resources to survive initially and thrive.
What I think is mostly necesary for a "race" of life forms to survive and thrive to rule a planet initially is a form of reproduction, whether it be asexual, sexual or other reproductive strategies the race may have.
this is the first key to survival and multiplies to create a race of aliens to actually be able to become advanced.
A single life form is not enough to manage an entire area, it needs help and team effort to be able to survive.
Take wolves for example, they usually hunt in packs in order to grab a meal, take their share and survive their daily lives.
However, it is scientifically proven that cells need some sort of breeding ground to develop, that breeding ground is usually water or other liquid compounds that other cells need to survive which exist in the universe.
If there is none of that on a planet, cells cannot reproduce and let alone evolve.