I can't remember terminology, and my answers won't be bang on, but I can help point you in the right direction. I did 2nd year business law in 2011, so it has been a while.
Big thing: There's lots to say about each of these scenarios... courses like these often want concise terms and phrases, based on notes/lecture points. You could go on and on about stuff that is correct, but the teacher might not give you marks for that. These courses aren't about real-world solutions... they just want you to show you know the terms/concepts covered. So anything I say or anyone else says might not be helpful for the course.
#1: "As-is" sale clauses only take you so far. There are specific term(s) you are looking for. I don't know if that term is "negligence", or something similar, on the part of the seller. There may be failure to disclose. There may also be an assumption in the contract that the land, though sold as-is, is safe.
"Decide for yourself" suggests to me that the land is being sold "as-is". It also indicates that the seller chose to withhold vital information that legally must be disclosed. If you took this further (depending on your course), this is reckless endangerment of anyone who enters the building. Criminal charges may be laid.
I would look through your notes to see what your teacher wants. He could be getting at "the core of the contract", which is to say: The core of the contract is that a building+land is being exchanged for a consideration (I assume cash). The contract was not fulfilled, as the building component of the contract was violated (there was reasonable assumption that the land was safe).
Because the sale was land + a building (I assume land + a building?), a number of things could be gone after: Fraud, civil suit for a number of damages as a result, loss of income if the building is being used for business, cost of repair/etc. The sale of land + a building tends to be a combined contract, so I'm not sure how much of the land's value could factor into recovered costs. I don't know if the buyer could seek a reversal of the contract.
The buyer did what he could to mitigate damages (I don't know if that's the correct terminology, as I only remember covering mitigation of damage as after-the-fact actions). The buyer hired an engineer, and did his due diligence to ensure all was well.
Anyways... there's more to cover, but to get the right answer that your prof may want... you might want to look at your notes.
#2: I'm not sure either, but I believe fraud involves intentional deception. I (think) Adam would have had to intend not to pay back John, or perhaps failed to notify John ahead of time when he knew it was unlikely he would be able to pay. Other factors that may matter might include what expenses Adam chose to prioritize.
Oral agreement is still a contract. It's just as enforceable as written if everyone is honest & accurate... but proof (someone could lie), accuracy (someone could recall the wrong words or selective parts of what was said), and interpretation (intonation and what is remembered), may differ... making oral contracts difficult. As far as this contract extension goes, it depends: What are the revised terms? All I see is he agreed to be paid later. The agreement could've been "sure, not a problem, pay me in a month? good?". The agreement could've been "well if you don't have the money now, pay me as soon as you get it." The former would sound more like a go-ahead for an extension (foregoing accrual of interest or damages), while the latter sounds more like a temporary solution (a temporary agreement that doesn't exempt or modify previous terms that have been violated).
This post was edited by Canadian_Man on Apr 20 2017 08:15pm