part = {{a, b}, {c, d}, {e, f}, {g, h}}
lenpart=Length[part];

Do[Which[
ipart==1,
Print[part[[ipart]]],
ipart!=1 && ipart!=lenpart,
Print[part[[ipart]]],
ipart==lenpart,
Print[part[[ipart]]]
],{ipart,1,lenpart}];

Do[Which[
ipart==First[part],
Print[ipart],
ipart!=First[part] && ipart!=Last[part],
Print[ipart],
ipart==Last[part],
Print[ipart]
],{ipart,part}];