Do Kanji have consistency in pronunciation like Chinese HanZi?


I learned to speak Mandarin a while ago and have understanding of Kanji thanks
to that. However, I'm new to learning and I'm tripping up over this, till I
wrap my mind around it. Do Kanji have several pronunciations?

For example. 日本. here it is "nippon", however, and when I see the second kanji
in 六本木, it seems to be pronounced the same. However, in another example like
今日 the first is pronounced "kon" here while in a sentence like 今何時ですか it is
pronounced as "ima".

My question is: Are these instances consistent at all? Perhaps when 今 is on
its own it's usually "ima" but when paired with other kanji it is pronounced
differently? Or is it inconsistent and you can find sometimes it is still
pronounced as "ima" even when paired with other kanji? Also, when two kanji
are paired, can the pronunciation of the word take a new form different from
how they are both separately pronounced on their own?

Many thanks!

