As mentioned previously the same thing that happens to your bank accounts, pensions, 401K, VISA CC, etc.. Only Bitcoin is better than those in that when a few Bitcoin "nodes" come back online with a generator/solar, etc. Bitcoin transactions can resume. Many thousands of nodes...each one have a complete record of all Bitcoin transactions since 2009...I am running a node at my house....I have got you covered! ;-)
BTW: if your 2nd Q is "what if the Internet goes down"...the Bitcoin network has been established on HAM radio and satellite.
While the power grid is out, gold/silver remain gold/silver. Same for ICE automobiles.
When (not if) the grid power comes back, gold/silver remain gold/silver. Same for ICE automobiles.
When (not if) the grid power comes back, IRA/401k/Roth/stocks/bonds/BTC may come back. Any one or more may not come back.
Now, replace “grid power” with “SWIFT/FIAT/FED/IRS/Income-taxes”...
Post apocalypse will your local warload accept bitcoin as payment?
Think about it.
Then cash out and buy rice and beans and alcohol, tobacco and firearms.