In other words, what prevents investors posing as home buyers to get an early offer in?

This prevents you from spending your Saturday morning in a vacant apartment for a tenant that doesn't show up and that happens all the time.

The differences between NOO and 2nd Home are pretty clearly defined and stating it is a 2nd home to gain the advantage of putting less down and getting a lower interest rate is what those fraud prevention measures are intended to stop. 

Your criteria is crucial because it helps an assignor focus on finding the right deals and it prevents us from ruining our reputation with sellers in the market.

The thing most likely to prevent you from getting many houses is going to be your debt to income (DTI).  

A reinstatement right also prevents the Mortgagee from calling the entire balance due.  

Always knew that some FHA's don't qualify but was curious to what were most of the root causes. 

There are no bi-laws preventing this currently.

How to prevent loosing a rental that's in tax sale with no money and tenets that need evicted.

I have found HELOC and refinance appraisals to be more conservative than purchase appraisals because they can be and not prevent a transaction from closing in many cases.