To my knowledge there is no version of Janis, so it would be Janis.
The closest equivalent in Irish Gaelic might be Sinéad (shin-aid);
for Scottish Gaelic possibly Sìne (sheena).
Iàcob in Scottish Gaelic Iacób in Irish Gaelic
Not all English names have Gaelic equivalents. In those cases the English form is used.
Foirfe or Beacht may be Irish Gaelic equivalents of 'perfect'.
Proper names are not 'translated' but the equivalents areScottish Gaelic, Eilidh MàiriIrish, Léan Máire
Proper names are not 'translated' but the equivalents areScottish Gaelic, Mà iriIrish, Máire
'Shamus' is an English phonetic spelling of the Irish Séamus and Scottish Gaelic Seumas which are equivalents of James.
Seasaidh/Seasag are equivalents of Jessie.
In Scottish Gaelic 'Eòin" is considered to be the equivalent of 'Jonathan'; Irish has 'Seanchán' which is close in sound. Both of these are 'equivalents' rather than 'translations', however.
Names aren't translated, they stay the same. True, but the names have 'equivalents/cognates' Irish would be Eoin or Seán in Irish and Iain in Scottish Gaelic.
The name 'Herbert' is spelled Hoireabard in the Irish.
"Please" loosely and "With your will" literally are English equivalents of the Irish Gaelic phrase le do thoil. One of the pronunciation possibilities is "leh dhu hull" in Gaelic.
Ian is Iain in Scottish Gaelic and means John; the Irish equivalents are Seán and Eoin.