Yes, you can apply for the CA Foundation Exam even if you have a gap year after Class 10 and then completed Class 12.

Eligibility for CA Foundation Exam:
To be eligible for the CA Foundation Exam, you need to fulfill the following criteria:
1. Class 10: You should have passed Class 10 or an equivalent examination from a recognized board or institution.
2. Gap Year: There is no restriction on the number of gap years after Class 10.
3. Class 12: You should have either appeared or cleared the Class 12 examination from a recognized board or institution.

Application Process:
To apply for the CA Foundation Exam, you need to follow these steps:

1. Register with the Institute of Chartered Accountants of India (ICAI) by filling the online registration form available on their official website.
2. Pay the registration fee and submit the necessary documents such as Class 10 mark sheet, Class 12 mark sheet (if available), and a recent passport-sized photograph.
3. After registration, you will receive a registration number and study material from ICAI.
4. Start preparing for the CA Foundation Exam using the study material provided by ICAI.
5. Once you are confident about your preparation, you can fill the exam application form on the ICAI website during the specified dates.
6. Pay the examination fee online and submit the form.
7. Download the admit card from the ICAI website when it is released.

Tips for Preparation:
- Create a study schedule and allocate specific time for each subject.
- Use study materials provided by ICAI and refer to additional reference books if needed.
- Solve previous years' question papers to understand the exam pattern and practice time management.
- Take mock tests to assess your preparation and identify areas that need improvement.
- Seek guidance from experienced professionals or join coaching classes for better understanding of concepts.
- Stay updated with the latest amendments and notifications issued by ICAI.
- Practice regular revisions to retain the learned concepts.

Conclusion:
Having a gap year after Class 10 and then completing Class 12 does not affect your eligibility to apply for the CA Foundation Exam. Follow the application process outlined by ICAI and prepare diligently using the provided study material and other resources. With proper planning and consistent effort, you can successfully clear the CA Foundation Exam and progress towards becoming a Chartered Accountant.