I plan to shift from CBSE to ICSE for 11th and 12th. Is this recommended as I’ve heard that ICSE is very difficult, but isn’t it all the same at the 11th and 12th level?

The portion will be the same. The exam pattern will be similar: Non- subjective questions. CBSE is more inclined towards questioning the concepts. ICSE will ask you to apply the concepts as well. If you do understand what you’re studying then ICSE shouldn’t be any different…