Yes, it should work as intended.
Yes, it should work as intended.
No, this setup won't work without BIOS flashing. The Aorus B450 AORUS ELITE is designed for older processors and won't support the Ryzen 7 3700X natively. For a compatible and affordable option, consider a budget-friendly motherboard like the MSI MAG B550 or ASUS PRIME B650.
Today's boards typically come with updated BIOS versions that support the third generation, which has been available for several months now. However, the B450 Aorus Elite isn't an ideal option because of its relatively weak power delivery system. It would be best suited for pairing with a 6-core R5 processor. I could suggest a more reliable choice if you have a specific budget in mind.
The MSI Max boards. The Elite isn't assured to include a compatible BIOS, and I don't expect it to be included because that would imply Gigabyte has sold many of these faulty units (if you're looking for an affordable option, the Asrock Pro4 is always a better choice since it's even more budget-friendly)
I created a basic setup for a friend using the same board about three months ago, which included a BIOS compatible with Zen 2. I believe most available boards perform similarly.