If Tiny Umbrella only has SHSH for 4.1 and 5.1 then those are the only iOS versions you can restore to.
You cannot use the SHSH blobs from another device. Each SHSH blob is specific to each device. the other iPhone on 5.0.1 is of no use in that category.
A tethered jailbreak is (now in iOS 5) really a semi-tethered jailbreak. But lets just call it a tethered jailbreak....k? they are the same thing in iOS 5. iOS 4 is a different story,.....but lets forget about iOS 4.
Tethered jailbreak:
once the device is jailbroken for the first time you must boot the device again with the tool you jailbroke with to get Cydia to work.
If you perform a normal reboot the device will reboot into a "none-jailbroken" state. This means everything works except Cydia, and anything installed from Cydia. Also Safari does not work in this state either, but there is a fix for that besides using a different browser.
The only way to get the phone back into its normal jailbroken state is to boot "tethered". This comes from the fact that you have to "tether" your device to your computer, hence the term "tethered jailbreak".
There are 2 ways to boot tethered and it depends on which tool you used to jailbreak with.
If you jailbroke with redsn0w, you will just plug in your phone, open redsn0w, put your device in DFU mode, then click the "Just boot" button in redsn0w and your device will boot into it fully functional state.
If you tether jailbroke with a tool called Sn0wbreeze, you would have to launch an application call iBooty, and do pretty much the same thing you would do in redsn0w.
iBooty will boot your tether jailbroken phone twice as fast as redsn0w....but I don't recommend using iBooty if you jailbroke with redsn0w or vice versa.
Untethered jailbreak:
Quite the opposite of what I wrote above.
Once device is jailbroken for the first time......you have nothing to worry about. You do not need to plug your phone in and tether boot it with the tool you used to jailbreak with. You can reboot your device just like you would normally. End of story.