The altera DE2-115 board user manual section 4.8 page 47 describes the GPIO expansion header. It is clear that it has 3.3V and 5V power supply.
However, it later says that "The voltage level of the I/O pins on the expansion headers can be adjusted to 3.3V, 2.5V, 1.8V, or 1.5V using JP6 (The default value is 3.3V, see Figure 4-17)."
(1) I am confused, why is 5V power supply provided if no IO standard goes upto that? Also, why have IO standard down to 1.5V when power supply provided only goes downto 3.3V? Certainly an IC that takes 3.3V won't work with IO of 1.5V. Am I missing something here?
(2) Even though there are clamp diodes on these pins of the expansion header, is it ok to use a 5V IC that shall have VOH(max) of close of 5V?