1. FSB 240-275, depending on the CPU, PSU, and cooling. RAM speed separately adjustable in BIOS.
2. See above.
3. Most likely.
4. Most likely.
My 2.6 runs stable on Abit IS-7 at FSB 266-270, using Antec True480 PSU and Alpha Heatsink. Additionally, I move a lot of air through my case...