Can I apply for a patent after the toy is modified?

No, because the toy itself is not your original, so you can't.

Conditions for applying for a patent:

1. An applicant for a patent for invention and utility model shall be novel, creative and practical.

2. The design for which a patent is applied shall be novel and not belong to the existing design. Moreover, it must not conflict with the prior patent rights of others, or violate the law, social morality or public interests.

3. China's patent examination system is: early disclosure and request examination system (substantive examination) are adopted for invention patent applications; Formal examination of utility model patents and design patents. (The so-called formal review is also called registration system or non-review system. The main contents of the review are whether the application documents meet the requirements and whether the invention is repeated. After publication in the Gazette, if there is no objection within the time limit, it will be authorized)

After everything is ready, it can be accepted on the same day and protected by law on the same day.