Here are my 2 cents on this,
1. As per IRCC, if your absence from Canada is more than 2 weeks, you are supposed to notify them via a webform about the absence and the date of return to Canada.
2. It is good that your BG and test are completed.
3. You will NOT be asked for FP as your BG is completed as FP are for criminality checks which are part of BG and not Prohibitions. However, you MAY be asked for an in-person or virtual interview before your LPP is marked completed. Like FP, it is also not for everyone, but few of the May applicants were called for the interview either for ID verification, travel history verification or to answer some questions the officer has regarding the application in general or around Prohibitions. All communications from IRCC (whether FP or interview request) are sent via email tot he email ID you gave in the application. For FP request, they give 30 days to complete the request, however the interview is on a specific date and the email will have the date you need to attend the interview.
4. At this point of time, Vancouver office is very slow and are scheduling Oath for March and April applicants with an Oath date in September so mostly unlikely that you would get the Oath scheduled in September, but you never know! They will send the Oath invite via Email. If it is scheduled for you in September during your absence, you can respond to the email asking for reschedule of the oath ceremony due to your absence and give them your return date. However, please note that it can delay your oath and some got a new date within an few weeks of returning and few are waiting for months, so rescheduling should be avoided as much as possible unless absolutely necessary.
5. Don't worry, ALL communications from IRCC would be via EMAIL to the email ID you provided on the application.