An eight-letter word cannot be made from four letters. T, I, E and S are not sufficient to make an eight-letter word without knowing what letters can be repeated and how often they are repeated.
TESTIEST could work if you allow three Ts.
Testiest and Sissiest
testiest
Aluminum
There is one eight letter word that can be made from these letters: increase.
There is no 8-letter word that can be made, there are these 7 and 6-letter words though:senegasagenesagonesgenoasgnosesgossanseasonsegnossenega
INTEREST
The only eight letter word that can be made from those letters is 'starting'.
Tomatoes is an 8-letter word made with those letters.
refinery
expelled
There is no 8 letter word that can be made from the letters in "in and out". Words that can be made from those letters are:aadaidanandantataudioauditauntautodauntdindintdodondonnadonutdotdunduoIidininnintoioniotaitnationnitnonodnotnounnunnutoatonouttadtantintotoadtontunaundounionunitunto
Armchair is an 8 letter word. The 7th letter is i.
Survives is an 8 letter word. Bruises, reissue, revises, revives, survive and viruses are 7 letter words.