How many hashes, ticks and blocks is one slot?

How many chain of hashes is everyone supposed to compute in one slot?
What are the values of hashes_per_tick, ticks_per_slot, hashes_per_slot, slot_time in Solana? I don’t see a concrete instantiation of these values in both Solana code and docs.
What is a shred in Solana?
How many blocks does one slot contain? Will the validators vote once per slot or once per block?

How will these values be updated as technology improves?
Suppose in another 2 years, more powerful machines come up, do all the validators need to upgrade their machines before updating these values?