Here are the answers for the Nouns table. Ready to try it?

--- First Declension ---
Gate (feminine): porta portae portae portam porta
Gates (feminine): portae portarum portis portas portis

--- Second Declension ---
Friend (masculine): amicus amici amico amicum amico
Friends (masculine): amici amicorum amicis amicos amicis
Boy (masculine): puer pueri puero puerum puero
Boys (masculine): pueri puerorum pueris pueros pueris
Field (masculine): ager agri agro agrum agro
Fields (masculine): agri agrorum agris agros agris
Gift (neuter): donum doni dono donum dono
Gifts (neuter): dona donorum donis dona donis

--- Third Declension ---
King (masculine): rex regis regi regem rege
Kings (masculine): reges regum regibus reges regibus
Body (neuter): corpus corporis corpori corpus corpore
Bodies (neuter): corpora corporum corporibus corpora corporibus

--- Third Declension, I-Stems ---
Citizen (masculine): civis civis civi civem cive
Citizens (masculine): cives civium civibus cives civibus
City (feminine): urbs urbis urbi urbem urbe
Cities (feminine): urbes urbium urbibus urbes urbibus
Sea (neuter): mare maris mari mare mari
Seas (neuter): maria marium maribus maria maribus

--- Fourth Declension ---
Fruit (masculine): fructus fructus fructui fructum fructu
Fruits (masculine): fructus fructuum fructibus fructus fructibus
Horn (neuter): cornu cornus cornu cornu cornu
Horns (neuter): cornua cornuum cornibus cornua cornibus

--- Fifth Declension ---
Day (masculine): dies diei diei diem die
Days (masculine): dies dierum diebus dies diebus