Is it permissible for me to work in collecting and entering data for scientific research as per the request of the primary researcher, knowing that the conditions of the funding body may differ from what he requests, and in the event that he asks to complete missing data hypothetically?

The default rule is that you should conduct the research according to the agreed-upon method, as "the contract is the law of the contracting parties." However, if you know that the researcher will cheat the granting body in this way, then it is not permissible for you to do so, lest you assist them in prohibited deception, for "assisting in disobedience to Allah is forbidden," due to His (the Almighty's) saying: "And do not cooperate in sin and aggression." Furthermore, writing fictitious, unrealistic data in research is a form of lying and deception, and it is absolutely impermissible to do so. It should be noted that working on preparing research for others is not permissible without qualification. What is central to the research and would be considered deception if done by someone other than the researcher is not permissible, but what is not intended and is not considered deception has no harm in it.