The letter ה sounds similar to an English H (/h/ in IPA), while כ/ך sounds either similar to K (IPA /k/) or similar to German CH (IPA /χ/). Meanwhile, the sound of ח was historically in between (IPA /ħ/), but most dialects of modern Hebrew pronounce it the same as the fricative כ. (And then there's ק, which most dialects of modern Hebrew pronounce the same as the stop כ, but which historically was IPA /q/, articulated further back in the mouth.)
No. Just if you put a dot inside it. If not, it should be like ch or ha or the Hebrew letter "ח" Bat in our days it's not so common to put a dot or use a "nikud"
So you just need to see the word and understand how you should read it.
In the word eat "אוכלת" you should read it "ha" like in the food "hummus".
Hope I helped (;