will the CFA be helpful to quant?

Search this forum for CFA related threads, this has been discussed before. Members here will be glad to help with further questions.
But to answer it once again:

No. CFA=for financial analysts in big banks. Quants=R&D, or working in small funds, where they don't give a damn about any exams, but how smart you are.
It has been the common belief that taking the CFA L1 would compensate for one's lack of finance experience or to show interest in. In fact, UCB MFE program often asks its applicants to take the L1 exam before making decision.
The direct benefit of CFA L1 in finance engineering is not clear. The time and cost of the exam is not trivial so one should have an idea of what they intend the CFA for.
Absolutely. And in my opinion, clearing the intermediate stages alone has no tangible benefit. If you plan to invest in it, make sure you intend to see it through.