Can zero-fee txs get into a block?

What happens if a transaction is set to have zero fees?
Can it get into a block?

Also, if you updated a coin’s code to accept zero-fee transactions, would this cause a hardfork?

(e.g. made tx’s in certain denominations return a tx.GetMinFee() of 0)

Why is two hours the maximum acceptable offset for Bitcoin blocks?

As far as I understand, Bitcoin transactions include a timestamp, but the only requirement is that they don’t differ for more than two hours.

But why two hours? For computers that are constantly synced via NTP, two hours seem like a very big difference. I would expect that a difference of 10 minutes should be enough.

Or, if this is about time zones and summer time, shouldn’t they be using UTC time?

farmers quest to exchange goods and services

i would like to know the possibility to use Bitcoin for farmers to change good and services without ever to use of Money. We are trying to set a network between local farmers and would like to use Bitcoin in exchange for our services.

Looking forward to hearing from you.

Deprecation error on mac

I’m compiling on mac, and I get this error:

unsigned char *SHA256(const unsigned char *d, size_t n,unsigned char *md) DEPRECATED_IN_MAC_OS_X_VERSION_10_7_AND_LATER; 

Why does this happen, and how do I fix it?