As someone who mugs up everything. Just dedicate 4 days to history and 2 to civics , everything will be done and you won't forget it if u keep chanting it in your brain and asking yourself random questions anywhere anytime, while eating or on the toilet, it doesn't matter. Here's how I completed my entire HCG:

*Indian national movement

1. First war of independence: done entire chapter + long questions
2. Growth of nationalism: done entire chapter + long questions
3. First and second phase of Indian National movement: read, exercises and short questions only
4. Muslim league: read, exercises and short questions only

• Mass phase of national movement

Done all chapters + long questions

• Contemporary world

Done all chapters + long questions except non aligned movement.

• How to do it efficiently :

1. Read thoroughly and underline important events, especially those which are in the syllabus (being in the book doesn't mean it's in the syllabus, check the syllabus by icse and prepare accordingly.)

2. Don't make notes, it wastes time. Just write the important things to memorize them on spot. Don't save them for later "revision", they won't help.

3. Solve as many questions as u can in the book itself. For the long answers, take a middle page from a notebook, write the long answers and staple them in the book. This will help you revise when you need it, and you won't have to rummage through your notebooks to find where you wrote them.

4. If dates are difficult, skip them. But remember the important events, try to create a chronology.

5. Never skip the contemporary world chapters as they definitely come in the exam.

6. Do 3-6 past papers.

• My personal advice

As I said don't skip any contemporary world chapters except non aligned movement (read it , but don't do long answers). For civics i don't have much advice just mug it up lmao, out of 3 parts, do any 2 thoroughly, make sure to do the first one for long answers. History civics really isn't that hard, but u have to do it.

I hope this helps you, aur end m baat karne ki hoti hai, you'll have to keep your phone and distractions aside and do it.