Why would you want to sell everything right now? If I had that much money I'd first think of something that I need. I'd run out of ideas after 10 m probably.
What would you do with that much fiat money? Why would you want to keel that kind of money in an inflationary currency.
I can tell you what I'd do with 100 m in bitcoin.
Sell 1m right now to start spending on the things I need. Keep 99m in bitcoin for as long as I can.
3) What would happen if you suddenly sent a hundred million dollars to several banks/financial institutions? Would the IRS be immediately notified? Would your accounts get frozen? How do you avoid this?
Yes, the IRS is notified even if you transfer 100k USD to a bank account. Above a certain amount bank has to send reports and in the EU it's probably something like 20k EUR, but I might be wrong since they're sometimes changing it.
Accounts don't get frozen just like that, but the bank would probably contact you to ask about it.