>>6
The difference is that both 判 and 流 have different (and more common) readings. Back when the Japanese imported kanji, they assigned multiple Chinese characters multiple readings and even dumped the same meaning on different characters (see 解ける・溶ける・融ける・熔ける or 思う・念う・想う・憶う・懐う）. Each of these has the same reading ('tokeru' and 'omou' respectively) but they use different kanji with their own original Chinese reading to do so.
Whenever you come across such a homograph, there's almost always a single most common kanji. In your case, 分かる is used 99% of the time (溶ける and 思う as per my examples). It's good to understand their individual readings and applications but you should avoid using 判る and 流る when you want to say 分かる (if that makes sense)