The longest I can manage are four-letter words
alphabet
The biggest word you can make with the letters e, r, t, a, I, a, and a is "airrate." However, if you consider common usage, "airrate" may not be widely recognized. The most common word using those letters is "air," but "arteria" is also a valid term, referring to a type of blood vessel.
You cannot make any seven letter words from these letters. The biggest words that can be made have four letters. They are:AgeeAghaGheeOgee
face paint acquainted availed
Sized
The two letters in the word MAKE that have the same number of letters between them in the word as in the alphabet are A and E. In the word MAKE, the letter A is two letters away from M and E is also two letters away from K in the alphabet.
The word inkiest can be made with those letters.
One word you can make with the letters I N S A T I A B L E is "antibasil."
inertia
Refuge
expert
The words:adept, apted, baked, bated, bepat, pated, tapedare all the acceptable five-letter words that you can make from those letters.