1. Yes because oral is considered by most to be no risk for hiv or by some a very low theoretical risk. You tested at 4 months twice, this is conclusive.
2. Oral quick is less sensitive because saliva has less hiv antibodies then found in blood making it less sensitive.
True, testing accuracy is based on timing meaning the more sensitive ones shorten the detection probability. And there's always the question was the instructions followed correctly.
Two oraquick tests at 4 months is conclusive.