Hi @skippingpiglet, congrats on L2 pass! Yes, timing is quite tight for L3, but it is possible with lots of focus in 4 months. It may be worth taking it slowly and aim for August, which gives you lots of time to properly go through and practice for the constructed response style exams.
To answer your question though, if you failed L3 Feb 2023, you can register for L3 Aug 2023. See our Journey planner article for more details.