Is it possible to use σκύλος instead of σκύλο in this sentence?
No it isn't, 'σκύλο' is the accusative declension of the noun 'σκύλος'.
Ο σκύλος πίνει = the dog is drinking (the dog is the subject of the sentence). βλέπω τον σκύλο = I see the dog (the dog is the object of the sentence, I am the subject). This is what is meant by the nominative and accusative case for nouns.
Wrote ' το σκυλί ' not 'τον σκυλο' difference please.
In case it was not accepted, it's because it wasn't there and has been added now. Either is ok, but "σκύλος" is the more common word and sounds better.