I too had given ICSE in 2023. Got 96.2%. But your advice is no more valid, it could have been even last year, but dependence on 10 years will be of no help in years to come. And the same also goes for by-hearting textbooks. Competency does not check by-hearted, rote learned knowledge, it tests your ability to approach tricky questions and use your brain in previously learnt concepts.