Sure, so I'll focus on partnerships since that is mostly where you will see at-risk limitations.
Assume I have a basis before losses of $50,000 in my partnership interest. Of this $50,000, $20,000 is non-recourse debt, $10,000 is recourse debt, and the remaining $20,000 is my tax capital account balance. For 2017, I have a loss of $40,000. To deduct this loss on my tax return, I must clear “3 hurdles”.
Hurdle 1: Basis limitation: I can't deduct losses in excess of my basis. Total basis is greater than the loss by $10,000 so this is no problem. The full $40,000 clears hurdle 1, reducing my partnership basis to $10,000.
Hurdle 2: At-risk limitation: Here, losses cannot exceed my “at-risk” basis. Non-recourse debt, does not count for this, so my “at-risk” basis is $30,000 (excludes the $20,000 non-recourse allocation). Only $30,000 clears this hurdle, and $10,000 is a suspended loss that I cannot take on my tax return this year.
Hurdle 3: Passive activity loss limit: Assuming this activity is one you materially participate in then this limit does not apply. If it is a passive activity, we can only take this loss to the extent of passive income. (see your review course or online for passive vs. active activities).
So let's assume that this partnership is an activity I materially participate in, and therefore hurdle 3 does not apply. I am only allowed to deduct $30,000 on my tax return this year, even though I had sufficient basis to absorb the entire loss. Because, $20,000 of my basis was not “at-risk”, I could not pass hurdle 2, and $10,000 of my loss is suspended.
At-risk limits are on the partner level, since they have no effect on the partnership itself.
As for your other question, I think its absolutely worth the $35 to take the exam early if you are ready. There is nothing worse to me than being 100% ready for the exam days before you can take it. $35 is a small amount considering the amount of time and financial resources you have invested in this process.
Maybe this explanation makes a little sense, if not let me know and I can try to clarify.