Is an employee sinful if they use the university's free internet, allocated to them as one of its affiliates, to serve their acquaintances by submitting online applications to universities, knowing that the university provides this service to the external community for a fee?

It is impermissible to benefit from the university's internet service except for what the university permits in accordance with its regulations. If it does not permit its use for applications to knowledge platforms, then it is not permissible. It is not valid to argue for the permissibility of use by analogy with other services, as the default rule is that it is not permissible to use the devices, tools, or services of an employer except with their permission.