1) English ASCII printables (charaters that form the readable text that you see on the screen) only require 7 bits to be stored and represented because there are fewer than 128 of them, but the full ASCII character set is 8 bits, or 256 characters.
Many applications that expect to be storing readable ASCII, such as internet mail or a text field in a database, don't bother storing that 8th, or "high order" bit. This is why you have to encode documents sent in mail to only use 7 bit ASCII. This is what you *may* lose if you cram a binary into a text field.
2) If you lose the high order bit, then no. The easiest way to find out would be to try it.
3) I don't know. Probably not.