Saturday Mac riddles 100

Here are this weekend’s riddles – a special centenary edition – to entertain you through whatever you’re now allowed to do.

1: Undo undo with a capital Z.

2: A 1912 studio with what sounds like grain in public transport has been on Macs since 1998.

3: A mass you may want to bar with a series of links to a distributed ledger for virtual riches. What am I?

4: Almost a utility, I illuminate various schools of thought rather than a unified log. What am I?

I will post the answers first thing on Monday morning.

Please don’t post your answers as comments here: it spoils it for others.