No, there is no problem. Their residence permit just needs to be valid for at least 3 months after your planned arrival date in France. The accommodation certificate is already extensively covered here.
To my knowledge, there is no fixed time frame for the issuance of the prior enrolment agreement or for the end-of-procedure email from Campus France. Depending on the demand, it can take from a few days to several weeks. Generally, Campus France does not provide appointments at the embassy; it is up to the student to schedule their own appointment.
If your blocked account can cover your tuition fees in addition to your living expenses, you do not need a financial guarantor for the sponsorship.
Hello @Cecilia_Kengne