I'll tackle a couple.
#1) Are there any values of x you CAN'T put into your function ? Doesn't look like it - pretty much anything will work for x.
Are there any values you CAN'T get out for f(x)? Look at that e^x. Can it ever equal zero? Nope - an exponential function can never equal zero. That means 3e^x can't be zero, so 3^x - 4 can never be -4. Based on that, I choose c.
#3) You're right - you have . That's the same as:
(remember when you divide powers with the same base, you can subtract the exponents; thus, you can rewrite a difference of exponents as division - that sounds a little confusing, but hopefully makes sense).
I'll leave it to you to simplify the above.
#4) Since it's multiple choice, I would just try plugging in both x-values into each of your 5 choices and seeing which function works (i.e., gives you the correct f(x) values) for the information you're given.