1. Yes, you can. That's probably the most-asked question in relation to FMCB...
2. Yes, he can. But he needs to have a PS2 of the same region (like spud42 said: Look at the last 2digits of both consoles.). You only need to burn a uLE-CD/DVD and start the FMCB-Installer for example from USB.
3. If your PS2 is an SCPH-900xx-Model and has a datecode of either of these: 8D, 9A, 9B, 9C, 9D, 0A, 0B, 0C, 0D, 1A, or 1B, it won't work.
If it is one with a datecode '8C', there is a 50/50-Chance and if it is one with 8B, or lower (8A or a smaller number except 0 and 1), it will work too.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux