Since Teotihuacan is a huge site (the majority of which is still not explored) what has been open to tourist is the result of several projects each contributing their part in trying to understand this city. In terms of restorations, some of the earliest work was carried out by Leopoldo Batres in the 1900s with his explorations of the pyramid of the sun and its adjacent parts along the street of the death. Although Batres is often attributed with using dynamite to uncover the pyramid the reality is that there is no clear evidence that he ever did that, and to be honest it sounds more like a smear campaign to damage his image. He more or less uncovered and consolidated the main facade of the pyramid as we see it today. However, when you look at the end result and compared with earlier paintings and photographs, you can see tat he actually took some liberties primarily with the third body of the structure. However, the majority of the central precincts of the city were uncovered and consolidated during the 1960’s Proyecto Teotihuacan. Part scientific explorations and part restoration efforts, the Proyecto Teotihuacan was a massive undertaking that focused on uncovering some of the most important buildings at the hearth of the city. This big project consolidated most of what we can see today.

In terms of the used methodologies, INAH (the government institution in charge of everything archaeological in Mexico) uses a plethora of well-recorded interdisciplinary and rigorous techniques that helped archaeologists navigate how structures were found and what consolidation/restorations were performed to each structure. So, from a scientific perspective we can trace back what each project has done to any given building. In fact, after each project is completed, they are required to submit a report to INAH stating everything that was done, including any consolidation efforts that were performed in the case that architecture was uncovered.

To answer your question about their use, the reality if that we can not truly say with certainty what was specifically going on at the top of big buildings at Teotihuacan. This is due to several reason, including preservation, termination activities (certain areas of the city are though to have suffered from fire events towards the end of their use) post-abandonment activities (it is known for example that the aztecs did some excavations and removed objects from Teotihuacan), and also the vagaries of archaeological research. Thus is is assume through analogy from other big constructions in Mesoamerica, that being very prominent buildings at the main part of the city the big pyramids were probably temples that housed ritual activities. Unfortunately, we cannot go beyond certain generalizations with a high degree of certainty. Furthermore, we think that not everyone was allowed to go up to the temples since they may have been considered of a sacred nature and their access seems to be very restricted.

Finally, your last question is somewhat incapable of being answered because it gets into the real of phenomenology, how people experience the world, which is a very hard thing to known with a great deal of certainty in the present, let alone in the past. I really enjoyed your enthusiasm and I will be very happy to answer any followed up questions that you may have.