I failed P1 in Dec 2017. Probably due to having too much to do at work & therefore not enough practice.
Is it possible to pass P4& P5 without the underpinning of P1/3?
If you are confident that you can pass both P1 and P3 before the introduction of SBL than I think you should clear these papers first. Remember that you must have pass both papers before the introduction of SBL otherwise you will have to attempt SBL.
yes you can attempt P4 and P5 before given P1 and P3. you can attempt any papers of professional level in any order.