Everything humans have ever built/invented/designed/created reverts to its natural state. All earthly resources (coal, oil, timber etc) return to the earth. All technology is gone, all tools must be recreated from scratch.

However, all currently living people remain alive. Intelligence remains, but only what is stored in the brains of those who are living. Records/books/ancient tablets etc are gone.

How long do you think it would take for the first group of people to return to a standard of living comparable to the modern middle class?

Tl;dr: All currently living people are transported to a period where technology is roughly that of ~10,000 BC, but they retain modern knowledge.

Hmmmm. Not so long imo.

Buildings is iron - steel...

Houses - Wood...

Tools... well that pretty easy to make if you already have the plan.

Maybe 10 years?

Hmmm. This is a very in-depth question. Sure, we have the knowledge of how to build buildings and how to acquire our resources, but we don't have any of the tools necessary to harvest the resources. And if we could broadcast a communication we could centralize the talent and minds necessary to start formulating a plan for how to begin reconstruction. However we don't have that anymore in this scenario, so let's say 10 people in the country know where we can find iron deposits. Okay, so the ten people have to travel to those locations, and then we have to get people willing to trust these random 10 guys in order to start digging.

Oh boy. This is certainly complicated. We'd also have to have more people dedicated to farming in order to produce enough food that people can start specializing again. Because at first, almost EVERYONE will have to start growing and cultivating their own food. And if you actually want to stay in an agrarian society, we could all live with reasonable ease if all we do is live together in communes. But that wouldn't allow us to have the level of medical care we have now, or the level of entertainment or diversified labor.

I think we could realistically get back within 100 years, at most. We would obviously have set-backs if people are unable to work together to pull us back into the "modern" lifestyle, though, so this is in no way a simple question with an easy answer.

I think you can compare this to a reset in diablo.

probably several thousand years
7 billion people need alot of food
and that would probably serve as the basis for systems of control and power

we would naturally assume that groups would form , and conflict between groups would start ( id hazard a guess within the 1st year )
groups that decided to spend their time and effort at trying to regain what was lost , would find themselves at a disadvantage against groups that decide to spend their time killing/enslaving other groups
i would think that the population would drastically drop , and with that drop , alot of our currant knowledge would be lost

I agree with the food aspect, there would be massive casualties. It would be interesting though, the casualties wouldnt so much be in underdeveloped countries, but in developed countries were they look on other countries for the food and other resources (American would have huge problems), not to mention underdeveloped countries may be more used to having to obtain their own dinners. For a period of time the developed people would be our underdeveloped.

However I do feel that it wouldnt take thousands of years. We are still given most of our intelligence, we know how everything worked up until now. Its just a matter of reattaining all the resources I cant picture more that a couple hundred years to get back to where we are today. You have to remember some intelligence is lost because nothing will be documented, communication will be at a 0 for a period of time.

do all the vegetable that are still in the ground being grown in our land disappear (i.e. cornfields in the midwest)?

You need to remember though, there will be reproduction of new people and the next generation won't have the memories of the ones who would be living now.

It would also be very difficult to explain it all to them when they haven't been brought up in it and can only go by lip service. Let alone the new generation trying to reconstruct what life would be like now from back then for them.

The first thing we would need to do is do all the farming and hastily build houses and build from there like old times. That may take a few years. After a base is established we would need to harvest the minerals while the building designers design the houses and all. Now how can we construct a steel building when we don't have the tools or bulldozers to help us build?

The first generation (In this case it would be us) would be all about planning and paving the way for the next generation to go forward with the plans. After the last of our kind is dead then eventually even after all the buildings are up an all that. There would never be the same kind of computer game ever again. Who would seriously come up with the idea of pornography or the internet? Who would come up with the idea of Diablo 2, Minesweeper or tetris?

My next paragraph is purely from my head and is an assumption of what I think would happen.

While we may go back to our modern way the world would never be the same again. As opposed to the time lengthiness I would say around 500 years. Breaking it down into parts. The first 70 or so years would be all about farming and building old-school houses as fast as possible. On top of that it would also be about gathering minerals and planning all the buildings for the next generation to go forward with the plan. for around the next 50 or so years it would be about building the tools that would help build the tall buildings and all of that kind of stuff. Building bulldozers and cranes. Designing cars for fast transport. After that is all completed we can finally proceed to build a skyscraper and remember it is the first time this has been done. Now on top of the skyscraper we'll build 1000s more and make a city. That will easily take over 200+ years. The next 100 years we would be well underway to getting back to our former glory. It would now be 'tying up the loose ends.' What I mean by that is now making improvements to old designs and making them better. The mobile phones can access the internet and have cameras installed. Even though we may have had them in mind way back in the first generation that would not have been a high priority without the communications tower where we can send and receive calls.

Now that is done the last 80 years is the advancement of the space age. Where we will be able to launch a rocket to the moon and be the very first people for the second time in history where humans have landed on the moon.

I'm not sure, but I would be writing mass How-to books until the day I died.

Like I said, the first generation would be paving the way for the next generation.