about the first question, if you are increasing your mileage gradually and keep that mileage consistently high, the answer is yes, if you only do it for a short time and in an iregular way, so the answer is no, you gotta keep that mileage high for several weeks to see if it applies to you.
for answer numbert 2, the answer is absolutely yes, only think that strides are benefitial in a flat terrain, just imagine what they can do to you doing them in a hilly terrain, plus i have read some training of the elites and rodgers rop incorpores hilly strides of 50-80m on hills. it does improve your economy, your form, your vo2 max, leg strength, etc. hope this helps.
cesar