I often ses a range in voltage for power input for example the 04 ver lilypad is like 2 to 5.5V I don't understand that. Is it faster if I increase voltage? Are some things turned off?
Is it a safety thing for power irregularity?
I'm a complete newb to arduino and programming/circuit design in general.
I haven't figured out how to determine what components can be attached to the boards; in my particular interest I wanted to attach a BLE Micro (AT Command) and a 3 or 9 axis accel/gyro/mag-comp sensors (I2C)
Also out of curiousity how can I determine what limits my peripheral connections? I can parallel wire certain pins right? A project I have in mind is a 5 point fingertip tracker that has a 9-axis sensor on the tip and custom electromagnets for distance sensing. I don't know if one of tbese boarda can support all of those peripherals, is 8MHz fast enough? I have a lot of reading to do and catching up.
As long as the voltage is within the specified range, it is expected to work. The speed will be the same (the maximum speed that it could run at is higher with higher voltage - but to run at that speed, it would need a different crystal/resonator and/or different fuse settings).
What voltage you choose to run it at will depend on your application. Many people run lilypads directly off a single lipo battery, so the voltage will range from 4.2v on full charge down to 3v for nearly dead battery.
If you have to interface with something that needs a specific voltage (for example, with a 3.3v wireless device, or a 5v 433mhz RF receiver), you might choose to run it at that voltage, so you don't need a level shifter. There are lots of parts out there like this.
If you have a specific power source in mind, likewise, that might dictate your choice of operating voltage.
Note that the Lilypad is somewhat unusual among arduino boards in that it does not have an on-board regulator - the input voltage is the voltage the chip runs at. On most boards, a voltage regulator is included, and a power input range higher than the regulator output is specified. Many arduino boards run at 5v off onboard regulator when powered through Vin/DC power jack/etc (see board docs) off usually 7~16v - though you can power the chip directly and bypass the regulator if you need to.