1. Virtually nothing is beyond the scope of Iranian capabilities, provided these capabilities are backed by technological cooperation with Russia and/or China. The window of opportunity in this regard is now wide open; all that is missing is the political will.
2. An aircraft in the weight class of the F-5, even if stealth, is useless in modern air combat. You need kinetic energy to give BVR missiles their range, you need significant electrical power generation for a powerful radar and sufficient computational capabilities, you need payload capacity and ideally a large surface area to deploy a self-defense system, and of course, you need payload capacity and range. And so on.
The optimal solution in terms of cost-effectiveness is the KF-21, which also has significant growth potential.
Iran has the capability, in cooperation with Russia, for example, to develop unrealized "dormant" Mikoyan stealth concepts based on upgraded versions of the RD-33 (RD-33MK/RD-33MK-35/RD-33MKM) and the avionics and weapon system of the MiG-35, and gradually "domesticate" them.