A technical Hanafi rule applies when a person remembers an earlier missed prayer but still performs later current prayers before making it up.
Their Fard validity can remain suspended rather than being immediately and finally decided.
The source's example is:
• an earlier Fajr is missed;
• while remembering it, the person performs later prayers;
• if enough later Fard prayers accumulate so that Tartib drops before the original missed Fajr is made up, those later prayers become valid;
• if the original missed Fajr is made up before that suspension is resolved, the previously suspended prayers lose their Fard status and must be repeated as Fard.
This is an advanced rule; the important point is that 'out of order' is not always resolved by a simple instant-valid/instant-invalid formula.