It can be translated in two ways, according to the emphasis you want to give to the sentence:
*PURCHÉ [congiunzione subordinante condizionale] "Ad Aekke Naekkepenn non sarà fatto alcun male, purchè tu risponda alle mie domande" = "As long as you answer my questions, Aekke Naekkepenn will not be hurt".
In this case, the emphasis is all on the condition. If the condition is not met, * will happen. In this case "Provided that/If you answer my questions, A.N. will not be hurt"
*FINCHÉ [congiunzione subordinante temporale] "Finchè rispondi/risponderai alle mie domande, non farò del male ad Aekke Naekkepenn" = "As long as you answer to my questions, I will not hurt Aekke Naekkepenn".
As you may notice, "finchè" underlines the duration of the event and is a synonim of "until, while" ("while you are answering my questions, A.N. will not be hurt" or "until you answer my questions, A.N. will not be hurt).
As I wrote those are not stand-alone conjunction but they are used to build secondary sentences, so you need a main clause to link them to. Unless you are answering to someone who "offered" you the main clause...
-"Mamma, posso andare a giocare con Aekke Naekkepenn?"
-"Sì, purché tu faccia tutti i tuoi compiti!" [condition] "No, finché non hai finito tutti i tuoi compiti" [time]
AND, PLEASE, ANSWER TO HER QUESTIONS OR THEY WILL HURT ME!