Hi!
It is definitely possible to get a 645 in GMAT Focus with 20 hours of weekly practice, especially if you are starting at a 615 score. However, whether or not you need to subscribe to TTP will depend on your learning style and how disciplined you are with your studies.
If you are a self-starter and are able to effectively use the free resources available to you, then you may be able to achieve your goal without TTP. However, if you find that you need more structure and guidance, or if you struggle to stay motivated on your own, then TTP may be a worthwhile investment.
Here is a breakdown of the pros and cons of each option:
TTP
Pros:
Comprehensive and well-structured curriculum
High-quality video lessons and practice questions
Personalized study plan
Access to a community of other GMAT students and TTP experts
Cons:
Expensive
Time-consuming
Can be overwhelming if you are not used to following a structured study plan
Free resources
Pros:
Free
Flexible
You can choose the resources that best suit your learning style
Cons:
Can be difficult to find high-quality resources
Can be difficult to create a structured study plan
Can be difficult to stay motivated on your own
If you decide to go with the free resources, I would recommend the following:
Use the GMAT OG as your primary source of practice questions.
Supplement the OG with practice questions from other sources, such as GMATClub and Veritas Prep.
Use the GMAT Focus Official Guide for a comprehensive overview of the Focus exam.
Join a GMAT forum or study group to stay motivated and get help from other students.
If you decide to subscribe to TTP, I would recommend the following:
Follow the TTP study plan closely.
Take advantage of the video lessons and practice questions.
Ask for help from the TTP community when needed.
Whether or not you choose to subscribe to TTP, the most important thing is to be disciplined with your studies and to focus on your weakest areas. If you can do that, you will be well on your way to achieving your goal of a 645 GMAT Focus score.
As for sharing an account with your friend, I would not recommend it. TTP is designed to be used by one person at a time. If you share an account, you will not be able to track your progress accurately and you will not be able to get personalized feedback.
I hope this helps!