Words with double t's:atticattachattainattireattitudebatterybettingbrittlebarrettebuttressbetterbitterbottlebutterbuttonblottercattlecassettecommitteecluttercottoncuttingdittodiskettedinetteetiquetteflutterfritterfatterfetteredfittedglittergutterhitterhotterjitterykettleknittedknottedlittlelotterylettermattermattednettedotterpatternpattypattedpottingpotteryputterpettedrattlesettlestutterspattersputterspittingsplittingspottedswattedslottedscattertattleutterlyvettedwittedkittenlitterbatteredpatternsbetterbottompermitted
* mastiff (a breed of dog)
No.
Ferrous.
None. There is no word with double Q (consecutive). However, there are words that have two (2) Q such as: equivoque. quinquennia.
Some words with FF:BaffleBluffBuffBuffaloBuffedBufferBuffetCaffCaffeineCliffCoffeeCoffinCuffCuffedCuffsDifferDoffDuffDuffelFluffFluffsFluffyGaffGriffGruffGuffHuffHuffedJiffLuffMiffMuffMuffinMuffleMufflerMufflesOffOffalOffedOfferOffsPuffPufferPuffinPuffsQuaffQuiffRaffRaffleRiffRiffedRiffleRuffRuffleScoffScruffScuffSniffSnuffSpiffStaffStiffStuffSufferSuffixTiffToffToffeeWaffleWhiff
Words with double t's:atticattachattainattireattitudebatterybettingbrittlebarrettebuttressbetterbitterbottlebutterbuttonblottercattlecassettecommitteecluttercottoncuttingdittodiskettedinetteetiquetteflutterfritterfatterfetteredfittedglittergutterhitterhotterjitterykettleknittedknottedlittlelotterylettermattermattednettedotterpatternpattypattedpottingpotteryputterpettedrattlesettlestutterspattersputterspittingsplittingspottedswattedslottedscattertattleutterlyvettedwittedkittenlitterbatteredpatternsbetterbottompermitted
* mastiff (a breed of dog)
aardvark
ammoniaammunitionbrimmingbummerchummeddimmerdrummerflammablegrimmergrommetglimmergrammarhammerhummerimmerseimmurejammedmammalpummelrimmedshimmersummerslammerskimmerslimmersimmerswimmerswimmingtrimmer
sayyid
buzzbuzzarddazzledrizzledizzyfizzfuzzfuzzyfizzlefrazzledguzzlegizzardgrizzlyjazzmuzzlenozzlenuzzlepuzzlepizzarazzsizzlewhizzed
Exxon
capuccino
Sayyid
No.
Function