They had to design a specialized verification function, which I imagine would be the easy way to break it.
The brilliant part of Bitcoin is that it uses very widely known crypto primitives - verification is the same as getting the right seed (you just happen to be told what the right seed is, rather than having to pay for it to be discovered).
You must be on drugs. There is no separate specialized verification function. It's the same algorithm for verification as for mining.
Correct; both Bitcoin and Monero use Hashcash as PoW, only differing in the choice of hash function. Verification is only different from a solution attempt in asymmetric (i.e. non-Hashcash) PoW, such as Cuckoo Cycle or (the poorly named) Equihash.
lolwut. There is no specialised verification function.