Hello, 

These are some of the best sites that provides you with efficient test series

• Learning App - Embibe
• Toppr
• Hashlearn 
• Exam bazaar-Free NEET Question Papers
• Study Companion
• NEET Free Online Practice and Sample Questions- Examrace
• ASK book.
• Etoos EDUCATION etc.,

Hope this helps ....  

Hi Anshul,

Some of the best free biology mocks that are available online are- 

1. Embibe - it compiles tests based on previous year trends, thus, covering topics of different difficulty levels under each subject.

2. Exambazaar - the platform provides free access to upto past 15 years papers', thus, the students can practice better. 

3. ETOOS - the platform hosts free tests series of selected, most important questions. The questions are solved by an expert faculty which provides the aspirants a chance to refer to the solutions for their convenience. 

4. GradeUp - this website is now quickly catchup and offers full length NEET mock tests on the latest pattern of the test. You can also practice questions subject wise for Physics, Chemistry and Biology. 

5. Youth4Work - Youth4work provides full-length NEET mock tests and subject wise NEET mock tests for Biology, Zoology, Chemistry and Physics subjects. The questions are prepared by NEET experts and contain a mix-level bag of questions and past years' papers. 

I hope this information helps you, all the best!