Is there any difference in the pronunciation of 게 (crab) versus 개 (dog)? Or do you just use context to know which one someone says?
One Korean friend says yes, one says no. Based on that, I assume if there was any difference in pronunciation, it's lost to history, or it's like a chinese tone. Considering how often Koreans misspell words with 애 and 에, I'm going to guess the former.
Your mouth shape should be slightly different. 개 is a wider smile than 게
Some dialects pronounce the vowels distinctly. Some dialects not so. Some dialects treat both the same and infer the word by context.